Why is my car so hard to start in the cold?

[Racer X]

Hey all,

First, a little background on my setup.

It's a 3.2L MTX, X2J ECU, 3.2L injectors, stock MAF, currently an ATX fuel pump, but the problem was there when I had a Walbro 155LPH installed.

So, here's what I'm dealing with.

In the cold, say, below 32ºF, it does not want to start. It's almost as if the engine is dumping tons and tons of fuel in, because the only way I can get it to start is to go WOT to cut the injectors and clear the cylinders. Then let go of the pedal, let it stumble a bit, WOT again to cut fuel, then let go...

...I tried to start it last night, when the temps were around 19 or 20ºF and by the 4th or 5th cycle, it finally fired up.

The warmer the temperature, the less this behavior occurs. In the spring and summer, this is totally a non-issue.

Additionally, and possibly related, if I stab the accelerator off idle, it will stumble a bit until the RPM's climb a bit, and then will rev fine. This happens in the cold and in the warm weather, MAF connected and disconnected. New plugs and wires didn't fix this stumble, and the coil pack is known good. I did try a stock coil, which didn't show a change in the off idle stumble when stabbing off idle.

Obviously I'm going to have to troubleshoot my way out of this, but if anyone has any ideas on where to look first, or experience with this issue, feel free to chime in.

Thanks much.

 

[boat]

Just thinking, how old is your battery? When it is cold and the battery is weak, it can cause an issue in starting. My red 94 was having that issue, found out my 800CCA battery was only showing 400CCA when they tested it. Replaced it and it seems to have fixed it.

What about your starter? How old is that?

I have a similar issue with my red 94 MTX, it stumbles in a lot of the same ways and haven't been able to diagnose what it is. I would be interested in knowing what fixes this also.

 

[Racer X]

Battery is 1 year old, the starter is 7 and tested good 3 years ago when I had a battery cable issue. Even before the new battery, this was an issue.

Just to be clear, it doesn't stumble while idling, cruising, or accelerating. It only stumbles if I stab the gas while at idle.

 

[DJSHO91]

Have you checked to see if there are any codes stored in the computer? You don't necessarily have to have a check engine light come on to have a code stored. It sounds like something is effecting the cold idle settings. This could come from several different areas, so a code source would be the 1st place to check.

 

[SHOtimer]

I had a similar problem with my SHO many years ago, replaced the ECT with a Ford one and it went away. I presume the ECU was getting incorrect temp from the old ECT and was sending the wrong mixture to the motor.

How old is your ECT?

Shotting from the hip on this - but if the ECU thinks it's a 3.0, but it's a 3.2, could it be outside of the parameters enough to cause this issue?

Doug

 

[zak]

ECT is a valid thing to check, there are temperature vs resistance tables out there (all Ford ECTs use the same curve (Mazda excepted).

Are you using a 10 tooth or 12 tooth starter?

My number one suspect would be a stuck or gummy idle air control valve (IAC).

 

[3d914]

Ditto on the IAC. Too much fuel, not enough air = too rich and stumbling.

 

[dohcsable]

My number one suspect would be a stuck or gummy idle air control valve (IAC).

it wouldn't idle at all if that was bad, been there done that a week ago


I also encountered the flooding at start when cold a day after fixing the IAC, it was just a little moisture had gotten to the connections of the DIS module.



sprayed some electrical connection cleaner in them, let it dry out, and it started right up. Figure might as well try everything thats free/cheap first

 

[Racer X]

ECT is a valid thing to check, there are temperature vs resistance tables out there (all Ford ECTs use the same curve (Mazda excepted).

Are you using a 10 tooth or 12 tooth starter?

My number one suspect would be a stuck or gummy idle air control valve (IAC).

The ECT sensor is an AZ replacement from 5 or 6 years ago... hmm.

Starter is a 10 tooth model.

Thanks for all the ideas everyone, I'll give these all a shot. I'm sure there's a resistance table for the temp sensors in the EVTM somewhere.

 

[SHOtimer]

The ECT sensor is an AZ replacement from 5 or 6 years ago... hmm.

I'm sure there's a resistance table for the temp sensors in the EVTM somewhere.

I remember a thread, probably several years ago, where people had problems with aftermarket ECT sensors. I couldn't find it, but found this:

http://www.oldfuelinjection.com/?p=28

Doug

 

[rubydist]

did you pull codes at all?

if the tps is sick, the pcm could think there is more air going into the engine than there is, which could contribute to your symptoms. that can also cause the off-idle stumble. a bad mafs can also cause those symptoms.

 

[intimdatr]

I would Agree on the bad TPS or MAF causing incorrect air metering leading to and rich start and stumble of idle. Also the TPS may need to be adjusted, i know theres a way to do it i just dont know how.

 

[St Louis SHO]

Id lean towards a bad ect first...

 

[SHOZ123]

Just disconnect the ECT and it will go into default mode.

 

[itwonder]

Bit of a guess without codes; but sticking IAC or CID sensor. Doubt it's the ECT.

 

[Racer X]

Two codes:

114 - IAT sensor out of range
116 - Engine Coolant (ECT) sensor out of range

The IAT is also an AutoZone replacement. Funny that.

IAC valve is known good, I've tested with other IAC's with no change in behavior.

 

[thundersho]

I would like to chime in here. I have a similar problem where the idle goes to 2000 to almost stalling out.. pulled codes and got tps and iac.... changed them and still does this but only when cold after driving it for 10 minutes it will idle just fine.... i pulled the iac and tps off my 94 since it seems aftermarkets seem to be hit or miss. They work fine on the 94 and the ones pulled from 92 work on 94..

 

[rubydist]

I have never seen a SHO that runs right if it has the 114 iat code, so you need to figure that one out. it may be the new sensor has infant failure, or it may be a wiring issue.

iirc, the ect sensor is on that same leg of the wiring harness, so your real issue may be a bad ground on that section of the harness.

 

[rubydist]

I would like to chime in here. I have a similar problem where the idle goes to 2000 to almost stalling out.. pulled codes and got tps and iac.... changed them and still does this but only when cold after driving it for 10 minutes it will idle just fine.... i pulled the iac and tps off my 94 since it seems aftermarkets seem to be hit or miss. They work fine on the 94 and the ones pulled from 92 work on 94..

iac and tps are definitely on the same leg of the wiring harness, so it appears you have a connector or wiring harness issue. check all the associated connectors carefully.

I used to have a Mazda pickup that had a heater fan connector issue - when it was really cold, the connector would not complete the connection, so no heater fan. when it warmed up enough to work on it, the connector worked fine. it was a real pita to hunt it down.....

 

[Racer X]

So, the replacement ECT sensor didn't correct the issue.

Also, IAT sensor seems to match up resistance values with the chart in SHOTimer's post.

Also, I replaced the TPS for ***** and giggles (I had a new spare kicking around)... nada, same behavior.

Back to square one?