Cold Start Problems Persist from 6 months ago

[Marccus]

1989 w/(about) 440K.

Upon a cold start (car left for more than 4-6 hours, overnight), the start is very rough, with a "rolling idle" (as Ford describes it). I have to chase the tach up and down so it won't stall. If it does stall, it is VERY difficult to start. After about 5 to 10 minutes the engine idles like it is new and can drive with no problem.

If I leave it for more than 4 - 6 hours, then it's back to the same problem. Less than 4-6 hours it starts fine with a perfect idle.

I've been chasing this for months. There are no trouble codes and today I got code 67, which is a NPS for the A/C which should have nothing to do with the starting problem.

I've replaced the IAB valve like three times in the last 2-3 years.

Cleaned the throttle body and MAF.

Replaced coil about 1 year ago.

Replace TBS about 2 years ago.

PS pump replaced 5 years ago.

Intake manifold cleaned and rebuilt about 8 months ago.

New fuel pump - 4 months ago

New water pump - 6 months ago

CPS, CKP, timing belt, PS belt, WP belt - 6 months ago.

Cannot detect any vacumm leaks.

[U]Slight Coolant leak[/U] - loss of pressure about 1.5 psi over 5 minutes, cannot find leak with pressurized cold test and soap solution. Maybe radiator plastic tank leak. Radiator is over 8 years old.

Secondaries still not working. Checked wiring from PCM to connector and continuity is OK. Replaced the entire secondaries mechanism (solenoid, cannister, etc.) three times with units from junked SHOs. Highly unlikely that all three are bad. Still trying to figure out this problem. This problem existed before the cold start problems.

Fuel injectors never replaced.

Cold start problems began when catalyst in cat began rattling around and realized the cat was blown. Welded in new cat but problem persisted.

Perhaps blown catalyst worked its way down the exhaust resonator pipe and jammed leading to higher back pressure?

If so, why does problem clear itself up after 5-10 minutes after cold start.

Is there something the PCM does different when the engine is first started and "adjusts" engine to accomodate this problem.

For instance, upon cold start, PCM sees high back pressure caused by catalyst and adjusts engine operation to accomodate this to run smoothly.

Will be installing new cat back (w/o mufflers) from ShoSource within several weeks.

Any ideas??? :braincramp:
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[NotSoSlowSHO]

Have you checked fuel pressure at the rails?

Also, certainly not the CAUSE, but have you ever actually reset the idle?

 

[St Louis SHO]

I had a pcm cause this issue. It killed the IAC circuit.

- James

 

[SHOZ123]

The PCM has a cold start table and generally is either turned off with the ECT or time.

There is richer fuel commanded and a different spark table too. The fuel mixture will lean out with time and temperature.

Don't know about the OBDI tuning but the OBDII will generally time out before the ECT setting is reached, ~140F. Usually under a minute then closed loop.

 

[rubydist]

It does have a timeout, but it seems much longer than 1 minute - more like 10 in my experience.

Does it seem too rich or too lean during this cold-start phase?

 

[Marccus]

It does have a timeout, but it seems much longer than 1 minute - more like 10 in my experience.

Does it seem too rich or too lean during this cold-start phase?

Too rich. I can smell the fuel during this time. Especially if the engine stalls, then it is very difficult to start (takes a long time when the engine is cranking) and when it finally does I can smell the fuel in that initial burst of exhaust that exits.

 

[Marccus]

Have you checked fuel pressure at the rails?

Also, certainly not the CAUSE, but have you ever actually reset the idle?

New fuel pump, but have never checked the pressure at the rails.

Have never purposely reset the idle.

 

[Marccus]

Perhaps I should try a new PCM.

It's just about the only thing I haven't replaced!!

 

[NotSoSlowSHO]

You are having a fuel delivery problem. That is easy to see.

It is either fuel control (EEC or PCM) or something mechanical. Like a bad fuel regulator.

You need to check the fuel pressure at the rails.

 

[Marccus]

You are having a fuel delivery problem. That is easy to see.

It is either fuel control (EEC or PCM) or something mechanical. Like a bad fuel regulator.

You need to check the fuel pressure at the rails.

OK.

But why does the problem only occurr at cold start?

The fuel pump is new. The cold start problem persisted after I replaced it.

I don't have a gauge to check the fuel pressure, so I'll have to get one.

Do you know where I can get one with the correct fittings to use on the Schrader valve assembly?

(I assume I have to remove the Schrader valve and screw a fitting (1/16" NPT male x 1/8" NPT female) into the 1/16" NPT female (?) port and then use a bushing (1/8" NPT male x 1/8" NPT male) that screws into the 1/8" NPT female port on the fuel pressure gauge.)

Do I have that right!?

The fuel regulator was replaced maybe 5 years ago.

 

[SHOZ123]

Perhaps the time out difference is due to the OBDI vs OBDII difference.

I would suspect a leaking fuel injector. Start the car cold, let it idle for less than 30 seconds then shut it off. Pull the plugs and look for a wet one.

 

[Marccus]

OK. I'll pull the plugs too.

Thanks.

 

[rubydist]

I would start with the idle reset procedure. This also will return the pcm fuel trims to 0%, which may take care of the 'rich at cold start' issue.

Its possible that you have an injector that leaks down when the car is off. This will bleed off the fuel pressure by allowing it to dump into the cylinder, which would result in a very rich condition at cold start. This would not occur during hot restarts, because it would not have time to bleed off. You could check this by testing fuel pressure at the rail in the morning (cold start) vs. after the car has been run.