91Q stalled and won't restart

[91QAZ]

I have been trying to diagnose a stall + no start condition on my 91 Q. Thought it was FPCU/FP issues, but not anymore, so I'm starting a new thread. Here's what happened: I was driving at about 40 mph, car stuttered/stumbled and died. Have not been able to restart since. Chain guides have been replaced per service history, Q has 92,000 miles and about 100 miles ago (maybe less) I did an underplenum/KS job with hose replacements and shortly thereafter replaced FI #1. At the same time I did the underplenum job I installed a Robert/NICO ECU.

Diagnosis steps so far: 1) inspected FPCU for conductivity/burns = no problems found. 2) bypassed FPCU w/ jumper from harness to ground = pump hummed louder, but still no start. 3) Tried foot-to-the-floor flooded start procedure = no start. 4) inspected all electrical connections I could find in engine bay = found plastic connector above drivers valve cover cracked (wire from that goes into valve cover - probably to the coils?), but had wifey hold it together to ensure conductivity = no start. 5) installed fuel pressure gauge = when key goes to 'on' I get 46 psi with FPCU connected and 51psi with FPCU bypassed. When key is turned to 'start' (engine cranking) fuel pressure gauge needle bounces, but is in the 50 psi range.6) checked ECU codes = code 55 = no problemo (my arse).

I know my FP needs to be replaced, but based on the above, it that does not appear to be the immediate reason for my no start (unless I'm still missing something).

If I were in Atlanta I'd be towing this thing to T3, and may not be far from towing it to the dealer now, but don't really want to give up yet. I'm going to try to find an inductive timing light I can borrow and check timing and spark signal using Wes' method. any other ideas?

Thanks,Tom

[91QAZ]

Here's some additional info that may be related. After doing the underplenum/KS/NICO ECU job (<100 miles ago) I took the car out for a test drive and after warming it up I'd nail the throttle and sometimes it would pull like it's supposed to, but a few times I got a pretty good stumble/stutter as it accelerated (rpms would drop fast and far, then pick back up where it left off). I also felt like I hit fuel cut off (My 91 Q has a stock 93 TCU) at high RPM (7100ish). I attributed this to the removed rev limiter of the NICO ECU along with stock 93 TCU.

After hitting what felt like fuel cut off at high rpm, engine would not accel over 3000 rpm. Shut the car off, waited about a minute, then restarted and no more problems. So I figured ECU reset itself and all was well. Drove it for about 100 miles, but didn't really get in it too much, then the stall and no start.

[maxnix]

did you check your MAF connector carefully?

AZhitman knows of a good independent shop in Phoenix.

[91QAZ]

Update:

I did check the MAF connector, and in fact the service history shows the MAF and connector were replaced at about 67,000. Tried jiggling the connector while cranking to no avail.

I am narrowing in on the problem, though. I pulled coil, boot and spark plug #2 (with wires still attached) and placed the plug against ground while cranking - and I got NO spark. But don't know why yet. I've been trying to follow the diagnostic procedures on FSM page EF&EC 131, but can't find "engine control sub harness 4 and 5" despite the lovely drawings in the FSM. Anyone know where these are and want to take a picture? Or alternatively, is there a more simple way to find the source of a no-spark condition than the manual describes? Seems like I've read several things on this board related to other issues that are not in the manual...

[Raxephon]

I've been trying to follow the diagnostic procedures on FSM page EF&EC 131, but can't find "engine control sub harness 4 and 5" despite the lovely drawings in the FSM.

Those are the coil pack harness's under the ornamental covers in the center of each valvecover.

[RobertsnewQ]

OK, now we're talking. You've ruled out a fuel supply problem if you've got full fuel pressure.

When you swapped the ECU did you check to make sure the ECU connector is plugged in all the way? It should seat fully against the ECU on both sides. It is a common problem of running problems after swapping ECUs.

Start checking ignition by looking for +12v at the coil connectors (not the power transistor connector on the valve cover - the ignition relay or something similar could be bad if there's no power there.

Also check the ignition and injector fuses and make sure they are all in place and functioning.


Modified by RobertsnewQ at 8:40 AM 2/26/2006

[91QAZ]

Anlasak, thank for the pics - much clearer than the FSM...

Robert, I did make sure the ECU plug was fully seated, but now that you mention it, I WAS getting an intermittent CEL on my first run after ECU install and THEN tightened the ECU plug and the CEL went away, and I don't recall if I got any stuttering after that.

I didn't get a chance to work on the car today - too much family stuff going on, but I'll start with the coil packs and fuses and go from there. I also need to do more reading/searching on NICO to see what the most common ignition failures are caused by... Thanks,

Tom

[squeefoo]

Search for CAS ( crank angle sensor) I remember those showing up dead here once in awhile.

EDIT: Try cleaning the connector first. It's on the front of the drivers cam cover.

[RobertsnewQ]

Yes - I had that problem - when I wriggled it, the engine died. If the CAS connector is at fault, you won't have injector pulses either. Check them with a noid light (another trip to autozone).

[Raxephon]

Yes - I had that problem - when I wriggled it, the engine died. If the CAS connector is at fault, you won't have injector pulses either. Check them with a noid light (another trip to autozone).

Is there anything wrong with checking injectors/spark via the method in the FSM?
Modified by anlasak at 2:25 AM 2/27/2006

[RobertsnewQ]

No, that works fine too. I like a noid like because you can just pop the injector connector off and plug it in, but that way works too.

[91QAZ]

CAS, CAS connector, injector pulse - thanks for the input guys. I've got some reading/research to do now. Got a busy week at work, so I won't be able to get to the Q until Thursday at the best, Saturday at the worst. I'll post results when I get them.

BTW, what's a noid light?

Tom

[Raxephon]

BTW, what's a noid light?

I like a noid like because you can just pop the injector connector off and plug it in....

Its basicly a small light that lets you visually see whether the injector is getting an electrical pulse or not.

[91QAZ]

WooHoo! Sqeefoo, you nailed it! CAS connector. I gave it a jiggle while cranking and she sputtered to life. I had a coil/boot/spark plug pulled from prior tests, and it was laying on the engine, and I can positively confirm that I had spark - easy to see. Obviously, she didn't run well with one plug out, but at least I have IGNITION. Wont have time to put it all back together until Saturday, but I am elated to have a diagnosis at least.

I've done some searching re CAS and found many references to sketchy CAS connectors, but have yet to find a best accepted solution. I know there is an updated MAF connector to help solve that problem, is there someting similar with the CAS connector? What have others done to fix this connector?

Many, many thanks to NICO and it's members - I wouldn't be doing nearly as much DIY on this car without you guys...

Tom

[squeefoo]

Glad I finally got to help someone!

Maybe people will listen to me now.

[91QAZ]

Well, pulled the CAS connector apart today, expecting to find a loose or split wire. Instead I found that the spades on the CAS were all pretty corroded. I used an exacto knife to scrape off all the corrosion and put dielectric grease on them and put the connector back on. Must be a good connection now because she starts right away and jiggling the connector does not affect the idle at all.

Thanks again for the help.

[maxnix]

Maybe people will listen to me now.

Yeah, but I still ain't drilling a hole in my floorbaord.

[squeefoo]

Yeah, but I still ain't [sic] drilling a hole in my floorbaord [sic].

You really mean transmission tunnel don't you ?