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Old 12-13-2011, 01:18 AM   #1
Fitzy
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Question B21FT K-Jet issues, Misfire at idle

So I am definitely a new comer to K-jet but have been doing a ton of research lately to figure this car out. Picked up a Bently Manual and have been sifting through K-jet.org and reading up on the Green books. Not everything has set in yet so here's where I start asking for a bit of help/guidance. I realize this is a bit of a read, but I've been holding off asking questions until I got a little deeper into k-jet. Now I have about half a clue

Issues: Warm start problems, engine sputtering and sometimes what sounds like a backfire IN the engine (detonation?) at idle.

Started off with the warm start cranking issues. Used a known good accumulator and brand new check valve. In-tank pump has been replaced at some point. Also threw in a new fuel and air filters.

Car actually ran for about 5min then died. Replaced plugs and fired right up. At this point I verified the warm start issue was gone, but after a few minutes of running the plugs became fouled. Check the cap/rotor to find some crud in there, replaced cap/rotor and threw in another set of spark plugs. Same thing again, fouled plugs.

At this point I played with the Idle mix screw a tiny tiny bit to no avail, gave up on that and swapped in a know good fuel distributor with injectors & new seals. Also took off the intake mani and replaced the PCV + all the the vac lines and hooked everything back up.

Same issues as previous. Took the timing belt cover off to verify timing to find the belt pretty stretched and off a tooth. Set to TDC and used a new belt. Haven't checked with a timing light yet.

Same issues persisted. Checked the Idle air via CIS jumper 1&4/2&5 which set idle higher than normal. Seemed fine.

Tonight I checked a bunch of random stuff. Ballast resistor 1.3 (bently says 0.9), Impulse sender 1.019k ohms (bently 950-1.25k) and Coil @ terminal 1 & 15 2.3 (bently 1.9). Not sure what those out of spec values mean yet. Couldn't get to the CPR to check resistance.

I realize the next steps (or my first steps should have been) to verify fuel pressure, check the dwell and measure CO but I only have access to a fuel pressure gauge at the moment. I've heard many things about CPRs and them getting clogged so I was thinking this was my next item to remove and clean out...any other ideas??


- Just for some side notes, the harness has been replaced with some sort of re-manned one, fuel pumps do fire when jumpered, new pump relay and regular fuses as well. Plug wires have not been replaced but they do look in good condition. Coil looks old and beat but does work. Does produce spark on all 4 cylinders.
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Old 12-13-2011, 01:32 AM   #2
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Oxygen sensor? Measure the resistance of the plug wires.

I am just throwing things out there. Sounds like you are doing a pretty good job with the diagnosis. Check the wiring to the impulse fuel relay (by the coil).

Maybe someone else can chime in who has more experience with troubleshooting.
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Old 12-13-2011, 10:48 AM   #3
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You've been uber patient so far, Fitzy. My hat's off to you.

It seems you have good fuel pressure if you're fouling the plugs up that quick. The fuel injector resistance is a bit high, but it doesn't seem high enough to warrant delivery of that much fuel. But then again, K-Jet is a very finicky system, so this could be upsetting things a bit.

I'm definitely curious about the CPR. With all that dirt and oil you mentioned finding in your air box, it's possible some junk found it's way there. I don't know about opening them up, as I've yet to see a place you can find the gaskets you need to seal it back up.

Also, coonmax mentioned the O sensor, which is easy enough to replace.

And one other post I read, maybe there's an issue with the thermal cut-off switch. I hadn't thought of this yet. Here's the thread (post #8 specifically):
http://forums.turbobricks.com/showthread.php?t=188654

I can see if mine has this and pull it for you, and maybe you can rig my CPR to work even though it's slightly different than yours.
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Old 12-13-2011, 11:10 AM   #4
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You really need to verify operating system fuel pressure. Without that, you will just be shooting in the dark. A very common failure on these KJet cars at the point in time is the CPR (control pressure regulator).

On any KJet car that is not running quite right, I always start with a fuel pressure check and verify correct operation of the CPR. If those check out then I go from there.
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Old 12-13-2011, 11:14 AM   #5
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Thx coonmanx. I'll measure the resistance on each of the plug wires tonight. Is there any good way for me to test the impulse relay with a multimeter? The wires themselves do appear to be in good condition.

I had also read something about the O2 getting clogged/coated with **** or even going bad so I disconnected it for a few starts and it appeared there was no change. Changing it would probably be a good idea but I don't think it affects the car that much at idle to 3k.

The wiring to the cold start injector IS a little wonky. The PO or whoever rebuilt the harness did have to repair a section of the wire which has 2 white and 2 blue/yellow wires...seems easy to screw up to me. Although the car won't cold start without it connected. Have not tried warm starting without it.

Tony, I put in your thermal switch already so I think that rules that out but I am curious about this thermal cutout switch. I'll look into it and see if I can either test it or bypass it.

CPR is still on the top of my list to remove. It makes sense that there is an issue there but then again so did everything else. What I really want is to find my problem and stop throwing parts at this thing, lol.
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Old 12-13-2011, 11:29 AM   #6
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The O2 sensor doesn't really come into play until it's well warmed up, takes a good 5 minutes at idle.

Your mixture is obviously really rich. All you need to set it is a dwell meter and 3mm long hex key. CO meter is for perfect tune, but dwell will get you 90% there which was fine for me for years. Seems to me you've done everything except that! No point blindly replacing parts until you've done a basic tune up.
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Old 12-13-2011, 11:40 AM   #7
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Thanks guys. I do have a fuel press gauge coming like I mentioned and I know I'm not diagnosing K-jet properly but I'm getting there.

Canuck, from seeing all your other posts I knew if you responded you'd would say fix my base idle mixture. Do you think this dwell meter will work okay? http://www.amazon.com/Actron-CP7605-.../dp/B00062YUUS
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Old 12-13-2011, 07:14 PM   #8
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Fitzy, I have the thermal cutout switch on my block...again, known good (at least with my K-Jet system). You're welcome to it if you find electrical issues with yours.

On that note, anybody know what size thread that would have in the block, so i can buy a plug to close that hole up with if I pull it?
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Old 12-13-2011, 07:14 PM   #9
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Old 12-13-2011, 10:08 PM   #10
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Thanks Tony. I might have to grab that microswitch off you while I am at it.

Guess I missed checking the basic stuff, one of the spark plugs wires has no resistance. Doh!
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Old 12-13-2011, 10:09 PM   #11
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Double post attack!
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Old 12-18-2011, 04:34 PM   #12
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Update: Changed some relays, and plug wires since there was a short in one of them and still no change. Fuel pressure gauge is on the way but hasn't made it here yet.

In the process of going through all the electrical tests that I need to but have a question about dwell...which connections do I tap into? I thought the white/blue wire (blue connector was the CIS grounding and the red wire (black connector) was the lamda tap in. Please correct me if I'm wrong but the reading i was getting was 84.7%. I need to adjust but just making sure I am in the right location.

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Old 12-20-2011, 11:06 AM   #13
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So I measured lamda dwell with the red wire (black connector) with no ground attached and the dwell is a solid 90. Unplugging the O2 sensor and then starting the car again will result in the same reading, where it should have defaulted to 45 iirc. I can lean the mixture out but I get to a point where the car will bog and stall, too rich and the car starts increasing engine speed. I did take my time with this and made sure not to make aggressive adjustments. Just to check I swapped in a known good computer and retested in the same fashion.

Still waiting for the fuel line to arrive to check pressure.

Couple more things:
-Frequency valve is on full time
-Venting PCV to atmosphere seems to make the car idle much better
-Checking timing is pretty difficult because it studders on idle and won't hold 900 rpm consistently
-Swapped known good system relay and impulse relay and no change observed.

-I'm using Bosch Copper plugs, anyone have anything bad to say about them? Maybe try the Platinums instead?
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Old 12-23-2011, 11:19 PM   #14
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Hmmm...is the frequency valve supposed to be on all the time?

Is the PVC box old? I haven't heard that affecting idle rather than having oil seep and spooge out of every seal. But, I wonder if it's completely blocked if that would do anything.
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Old 12-23-2011, 11:34 PM   #15
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Don't put a platinum plug, the coppers are just fine. The freq valve runs constantly as it is what adjusts the fuel mixture per 02 sensor when car is warmed up and the ECU regulates it also.

Fuel pressure test, that's all I can say. You are wasting your time otherwise.
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Old 12-24-2011, 01:00 AM   #16
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well, it seems he's been planning on that but is still waiting for the hose and gauge he ordered.
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Old 12-24-2011, 09:23 AM   #17
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Still waiting on this damn fuel line to check pressure but in the meantime I changed the oil and put in a new O2 sensor. The sensor in the car was not outputting any voltage. I swapped OEM plugs that were in the car from the PO and it actually ran much better with no misfires! The bad thing is I looked up the PN on those plugs and they are NA plugs.

The PCV box is brand new, as far as I can see the only leak from this motor is coming from a bad o-ring on the turbo oil return line.
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Old 12-24-2011, 11:59 AM   #18
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Plugs gapped to .028?

There have been big discussions on here as to what plugs to run. Some say to only run copper. Me, on the other hand. I have been running platinum plugs since I got the car. I originally ran AC Rapidfires but now have a set of Bosch Platinum Plus in there. My mechanic informed me that the spark on these cars just isn't hot enough to require platinum plugs. I have experienced no issues in running them but it is not necessary. Having good plugs and having them gapped properly is probably the main thing.

What are the plugs that you have in there right now? If they are working then I might just leave them in there. Also are they hotter or colder plugs than what is suggested?

Checking the fuel pressure is definitely the next step. Also you might want to head by k-jet.org and see if you can download one of the K-jet diagnostic greenbooks if you haven't done so already. That can step you through all kinds of diagnostics.
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Old 12-24-2011, 12:20 PM   #19
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Thanks for the response on the plugs. I have 3 sets, 2 Bosch coppers and 1 OEM NA 240 Plugs that came in the car when I got it. Don't know if those are hotter or colder though. All are gapped correctly at .028.

The greenbooks have been pretty helpful as I have been going through them. Nothing has really jumped out based on those tests besides a slightly high resistance on the ballast resistor and that I have no dwell reading (90) from the car with the o2 plugged or un-plugged.
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Old 12-25-2011, 07:45 PM   #20
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I second everything Andy is saying. Fuel psi gauge and dwell meter are the 2 most important tools when working with k-jet. I do understand you are trying to get lucky while you wait for your gauge to arrive.

What is the history of the car? Been sitting?
If so I have seen fuel disty's and/or cpr's go bad (most likely gummed up inside from old fuel) after sitting for several years.

In my experience with b21ft's, they don't like cheap platinums. Stick with a basic stock temperature Bosch or NGK to get it running properly. You can go 1 or 2 steps colder later if you modify it that far.
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Old 12-26-2011, 04:28 AM   #21
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Quote:
Originally Posted by Fitzy View Post
So I measured lamda dwell with the red wire (black connector) with no ground attached and the dwell is a solid 90. Unplugging the O2 sensor and then starting the car again will result in the same reading, where it should have defaulted to 45 iirc. I can lean the mixture out but I get to a point where the car will bog and stall, too rich and the car starts increasing engine speed. I did take my time with this and made sure not to make aggressive adjustments. Just to check I swapped in a known good computer and retested in the same fashion.

Still waiting for the fuel line to arrive to check pressure.

Couple more things:
-Frequency valve is on full time
-Venting PCV to atmosphere seems to make the car idle much better
-Checking timing is pretty difficult because it studders on idle and won't hold 900 rpm consistently
-Swapped known good system relay and impulse relay and no change observed.

-I'm using Bosch Copper plugs, anyone have anything bad to say about them? Maybe try the Platinums instead?
So, if I'm understanding this right, your dwell readings on the frequency valve are 90* no matter what? That's definitely a problem... dwell should be 45* with no o2 sensor input, and fluctuate around 45* with a good o2 sensor input and correctly set idle mixture. at full frequency valve duty cycle, afr's are probably in the 9's or something incredibly rich like that. No wonder it's fouling plugs. Sounds to me like your frequency valve is borked.
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Old 12-26-2011, 11:37 AM   #22
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GrpA - The car had been sitting since 07 when the PO bought it in September of this year. He did some work to it and made it run (idled @ 2k though) but there were alternator and warm start issues. I bought it in early November and replaced the alternator, fuel filter, accumulator and fuel pump check valve then went on from there. Supposedly he cleaned out the gas tank and replaced the in-tank pump. I'm hoping the CPR is just gummy as you mentioned or the little filter is just clogged. I have another as a spare (-123 w/vac lines, mine is the -128 w/o vac) but I'm not going to remove that until I hook up the fuel gauge to check pressures.

iwannadrive - You are correct no change in readings (red wire). Also the fuel dizzy, injectors and freq valve are from another car that was known to be in good condition and only sat for a few weeks before I got it. When I swapped all of those over there was zero change in the engine misfire. Found the #4 injector was a bit lazy, all the others were in pretty good condition.
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Old 12-26-2011, 11:41 AM   #23
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If the CPR is knackered, the car will never go into anything resembling a duty cycle.. Just for what it is worth. Those 128 CPR's are pretty commonly bad too.. I have two dead ones sitting here right now.
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Old 12-26-2011, 02:07 PM   #24
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Quote:
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If the CPR is knackered, the car will never go into anything resembling a duty cycle.. Just for what it is worth. Those 128 CPR's are pretty commonly bad too.. I have two dead ones sitting here right now.
Go bad...like not fixable or more along the lines of the electronic element inside is just dead?
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Old 12-26-2011, 02:09 PM   #25
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My suggestion is to disconnect the cold engine cutout switch. It's the one just above the starter with the one gray or white wire going to it. That thing makes the dwell about 80 degrees or so if I recall correctly and even in the cold weather of your area that is too much fuel for a cold engine. Thus fouling your plugs. Plus if it's not working or stays grounded it's making the mixture too rich. After about 8-12 minutes though. It is supposed to go into closed loop. So some signal on yours is blocking closed loop. If there isn't a signal causing it. Then the mixture adjustment could be so rich it is blocking closed loop operation.

With the dwell gauge connected and a cold engine from sitting overnight the normal startup dwell is 60 degrees. Then it'll lower to about 50 degrees after a couple minutes. It will try and sample the O2 sensor after a few minutes but it's usually still too cold to work. Don't adjust the dwell until you know you have a fully warmed up engine. If it's not going into closed loop. Check out the connections for terminal 7 which is boost enrichment and the thermal cutout swith and connections for terminal 11. If your car uses the cold engine vacuum enrichment acceleration mounted on the firewall. That being grounded will override any closed loop operation and cause fouled plugs and super rich operation. The dwell will be about 90 degrees with that grounded. It goes to terminal 11 which is a ton of fuel.
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