Stumbling '91 Talon ESI - advice wanted

Hi,

A couple of weeks ago my 1991 Eagle Talon ESI (no turbo) developed a
pretty bad stumble across the RPM range. So far I haven't had any luck
trying to troubleshoot it...

Here is what I have tried so far:
- New plugs (old ones were pretty "worn")
- New fuel filter (had been a few years)
- Compression looks great (180 Psi on all cylinders)
- Checked the impedence of the plug wires and tried moving them around
- they appear to be fine (no change to the car's stumbling while
moving the wires and impedence was good)
- Checked the impedence of the throttle position sensor (TPS) across
its range - nice and smooth, no jumps
- Idle switch works (didn't expect that it was bad but it was easy to
check)
- Refilled the car with premium gas and added a bottle of injection
cleaner (in case of bad gas).
- Timing appears to be fine (around 5 deg BTDC) and no sign of erratic
flashing
- Checked the intake hose for cracks, looked for loose vacuum lines
(none found)
- Timing belt appeared to be in good condition (no missing teeth) and
cams appeared to be aligned
- I tugged and reseated quite a few of the engine bay connectors in
case of a loose connection, however there was no change.

What else should I check?

The car had been driving fine up until the day before this problem
occured, however I had noticed that it has become reluctant to start
in the morning, often stumbling and dying on the first attempt, but
normally ok on the 2nd attempt. The only strange thing I observed on
the day before was that the car would stumble probably once at around
2,000 RPM, but be fine over it. The following day it stumbled across
the entire RPM range.

When I changed the fuel filter I expected to get sprayed since I
hadn't released the fuel pressure, however there was only a couple of
drops that came out when I removed the outlet hose. Could this be an
indication that my fuel pressure regulator is bad or is it more likely
to be something else? (injector stuck open?)

I thought the apparent lack of fuel pressure might be why the car is
now reluctanct to start...

Any advice in troubleshooting this problem would be greatly
appreciated!

Thanks,

Greg

 

I am not familiar with your vehicle, but suggest you replace the plugs and
wires if they were not done recently. If that does not fix the problem,
then you might want to do an online search to see if the Engine Control Unit
(ECU) used for that vehicle in that year had the infamous electrolytic
capacitor leakage problem.

(Background: I had a similar experience just recently with my 1991
Mitsubishi 3000GT (133K miles), but the only difference is that the problem
came and went at random times and when it ran poorly there was a terrible
smell of unburned fuel in the exhaust. I did some web research and found
out that the ECU for the early model years had used 4 electrolytic
capacitors that were prone to leak and cause problems. I bought high
temperature versions of the capacitors for about $4 from an online source
and then removed the ECU, opened it and discovered that 2 of the 4 were
indeed leaking and had caused a short across other components. I went ahead
and replaced all 4 components and thoroughly cleaned under all the devices
and the areas of the printed circuit board that had been damaged using
distilled water and some liquid detergent. After rinsing the area
thoroughly with distilled water and drying it out, I then soldered the
replacement parts in and re-assembled and then re-installed the repaired ECU
and now everything is fine once again.

Good luck.

Bob

 

Thanks Bob,

I hadn't heard about that...

I believe the Talon is from the same factory as the 3000GT and has some
common components. I bet the ECU has a similar construction in both cars and
might be prone to this failure as well!

I believe I have a spare ECU (moved recently and don't know where it went!),
so perhaps I will try that to see if it solves the problem... If so, I will
open my original ECU and see if I can repair/upgrade it as you did...

I did replace the spark plugs (they were in pretty bad shape) and checked
the plug wires with an ohmeter and checked for shorts damaged insulators -
everything appeared to be fine.

Background - my car has only about 95,000 Km, being driven seasonally and
not at all for the last 4 years. I have now had the car back on the road for
the past 1.5 months, but the problem only showed up this week.

Thanks!!!

Greg

 

I have re-capped a few audio amplifiers and even one motherboard but this is
the first time I have ever heard of someone re-capping a car ECU. I guess
there is a first for everything.

 

inspect the plug wire boots for anyvwhite cualkey marks that might be
current escaping the boots talons have a tendecy to do this at higher rpms
and not at idle so they seen ok has the timing belt been replaced?could it
have jumped time