91 ES rough idle when cold

My wife has a 91 Daytona ES 2.5 Auto, no mods other than a new head and $150 fuel pump (ouch!). I bought the car with ~96k on it. The guy I bought the car from teaches/taught a H.S. auto mechanics class locally and he rebuilt the motor at ~80k. When I got the car it seemed fine, but it slowly get worse. When it's started cold it shakes REAL BAD and almost sounds like it runs on three cyl. for a few seconds and idles at about 1500rpm for about 30 seconds then smoothes out. This got worse and worse until the head cracked between the valve seats on #2 & 3. Put a new head on it and it was fine for a week or two. Now it's slowly getting worse again. The guy a bought it from said he put in new rings, pistons, and a crank kit. I think he mentioned the plug wires too but I'm leaning towards the distributor as the culprit.

Suggestions Plz/Thx?

very possible - check it out - take the distributor off an see if it looks old you can tell by the wear....

Well, I'm still stumped. I looked at the distributor and didn't see anything wrong, except for one of the ends (points?) not being pushed through all the way, but I think it was fine because they go in more than enough to make contact. This distributor is weird, I've never seen one where you could pull the points right out of the cap by pulling on the boot, it's like the points ARE on the ends of the plug wires!?

I don't think it was the problem now.

Let me explain what happens when I start it. When I turn the key it turns a few times and fires up then idles around 1500 for a few seconds then the idle drops to around 900 and it gets REAL SHAKY and almost sounds like it runs on three cylinders. After about 10 seconds it smoothes out and runs OK.

It doesn't do this after the first time it's started that day, unless it has sat for hours and hours, WTF?

It has a single injector on the TB, so I know it's not multi-port FI, unlike my Cavy which is MPFI and gets the occasional dirty or leaky injector.

Please give me any ideas you can think of as to why this beast shakes so bad, thanks!

28 views, one reply…
No one else has had this problem with 2.5 NA?

what does it idle at after it smooths out? does it stay at 900 or does it go up or down? do the plugs have any kind of fouling or anything apparent? i dont have any real ideas what it could be but maybe more info would trigger something with someone

When everything shakes away it idle's fine at 750, plugs are new!

Actually, when I start it it starts at about 1,500 PRM then as it drops to 900 it's starts to shake and miss. From the time I turn the key till it's smooth and idle's around 750 is about ten seconds, but it's shakes the worst for the first five seconds.

Anyone else had this problem before?

When the head was replaced, did you replace the gasket also? My guess is that the head gasket had gone bad, which caused the cracked head. Check the headgasket to see any signs of wear/cracking. When me and my dad shaved the heads on an old 360 we had, the heating of the head caused it to expand and crack the gasket. Maybe you tightened the head a lil too much and it is putting too much pressure on the gasket? This is just a suggestion.. but my spirit with a 2.5 does the same thing, and I'm pretty sure that's a gasket going bad.

my vote is head gasket, miss would be coming from water in the cylinder, do a compression check and a cooling system pressure check

When I had the new head put on we replaced the head gasket, bolts, plugs, oil/filter, coolant, and trans fluid. I had a mechanic do the work so I'm sure he didn't over tighten the bolts. It doesn't blow white smoke or any smoke at all so I don't think that the head gasket is the problem. The exhaust does smell a little rich, maybe it's starting way too rich and it can't fire all four until it leans out. What might cause this?

Hmm, IF it HAS been running too rich could that cause excessive heat around the valve seats but NOT cause the motor to overheat due to the fan constantly running?!? When the last head cracked it was a slow process, it took 6 months for it to crack bad enough that it blew the head gasket. My wife was driving when it happened and I was not with her but she said the temp. never went past 3/4. Is the 2.5 crap?

Scroll down to the first pic on this page and read-
http://www.thedodgegarage.com/turbo_ignition.html

This sounds very much like the shutter wheel. Also it could be just a bad Hall Effect Pickup.

Thanks! Time for a new distributor huh? What is a bad Hall Effect Pickup?

Thanks! Time for a new distributor huh? What is a bad Hall Effect Pickup?

Eh, if you just super glue the shutter wheel down it should hold for awhile.
The hall effect pickup is the thing right underneath the cap and has two connector's coming out of it and they plug into your wire harness.

All jokes aside....

Check the TPS sensor, and the head gasket again.

I can't tell you how many times poor workmanship and lack of education has killed so many 2.2 and 2.5's.

Most "mechanics" and I use that term VERY loosely(and for those of you who might be offended, sorry!) don't know enough to change head gaskets, nothing about re- torquing them, no clue about the machine work that was done, and simply aren't given enough time to do the job, let alone time to learn how to do it right.

In this particular case, the hall effect/shutter wheel or TPS as well as the head gasket can cause this. There are other possibilities too, but these are the most common.

I'm NOT a mechanic and I'm not offended, LOL! The guy that rebuilt it before I bought it was an auto tech teacher and I believe he did his part right (should have fixed the dist), I just hope it's a dist prob. As for the TPS I don't think it would be causing the problem because it drives fine, just starts like sh!t. Thanks for the info, I will try these things and get back.

The only reason you would need to re-torque them is if you used head studs. I use mopar performance head bolts and gasket, torqued to the standard 45/65/65 1/4 turn in the correct pattern and never re-torque them. I run 20 PSI daily and have a heavy foot, I've never blown a head gasket.
Oh, please tell me you are not using fel-pro head gaskets....they are notorious for blowing. If it's not smoking or overheating I doubt it is the head gasket though.

Well, I know it NOT the head gasket cuz like u said, it's not blowing any smoke.

OVERHEATING?… after taking the distributor to advance the guy show me some white spots on the wires (Mopars, BTW) he said I should replace them and the rotary button and that the coolant temp. sensor may be bad, proving my theory correct about it running too rich. If the sensor is telling the ECU the motor is colder than it REALLY is, then when the head cracked/gasget blew before, it DID get hot, but the gauge never went above two-thirds, because the sensor is malfunctioning.

So it is this that caused the damage to my wires, sound reasonable?

I told her not to drive it until we fix it, she can't anyway without wires on it,LOL!

'course I don't have the money to fix it yet but, I just got paid! Life sucks! I work hard 40 hrs a week only to send it all to someone else's pocket. Remember…

IF THE WORLD DIDN'T SUCK, WE'D ALL FALL OFF!

The coolant temp sending unit and sensor are 2 totally different things on these cars.

Also, the cracks between the valve seats are considered a fact of life with these cars, especially the turbocharged ones. They do not negatively affect anything.

I say get the TPS checked and replace the HEP.

Thanks for the reply, like I said, 'till I get money it'll sit for a few weeks.

If it was the TPS wouldn't the thing run just as bad after warm up and while driving? I runs great after the shaky start. I'm not an expert but I do have a good understanding of what many parts do. I was curious one day and I took the TPS of my Cavy and it didn't look user serviceable. I put it back on and when I turned it on, it idled high for a minute, I shut it off, started it and it was fine. I guess the ECU had to reset itself. It just spooked me so I don't want to mess with the TPS on hers.

I'm not too knowledgable about TBI cars, but on turbo cars we have a AIS sensor that when it's first started gives a spuratic idle but the engine runs completely smooth once warmed up for 15-20 seconds.

PWMAN, what's the AIS (air intake sensor?)

SVT Cobra306, that's right, I think he said the temp sending unit, not the sensor. How can the Hall Effect Pickup go bad and (feels stupid) what does it do besides hold the dist. I know it has the two/three wires on it and the connection is in good condition but it looks like all the wires all ground to the HEP, as if it was one wire!??

The Coolant Temp sensor is on the thermostat housing and it's the one the computer uses to read engine temp. The small one on the front of the head is the sending unit for the guage, mine doesn't even have one of those anymore-it has an autometer sending unit hooked to my autometer guage.

The HEP tells the computer what RPM the engine is running and is very important to the motor running properly (timing, injector firing, etc.) Usually if it goes out, the engine will simply not run, but it could cause other issues.

When was the last time you did a good tuneup and changed the fuel filter?

WOW! It's been awhile… I finally got 'er running, bought new wires, dist. cap, rotor, and plugs. It's starts much easier and dosen't sound bad at all like it did. It does have an occasional miss when cold, can't tell if it's one cylinder or if maybe the injector is dirty from sitting, but it's not as bad as it was.

The points on the old wires were burned BAD! The rotor was worn down a little too. I couldn't get Mopar wires from Advance Auto, they said I'd have to go to a dealer, F**K that! So I got the Autolite Professional Series, they have a LTD lifetime warranty so if they burn I can get more for FREE!

I got the timing pretty damn close to perfect, but it feels like it's not putting all the power to the ground. It used to jump off the line like out like a bat outa hell! Now it takes a second to get moving, but the motor sounds strong. ? I think it's just where it sat for a few weeks, she drove it around for awhile today and she said it's a litle better but still lacks the power it had. Does anyone know what might cause the tranny to lose power? Maybe the timing's barely off and the ECU is doing something? Help!

It did not have this problem before we fixed the ignition problem, why is it doing this?

if i was you i would change the tps i took my car in to get check due to other problems the happened which i wont get into and the guy at the dealership said i had to change it other wise i was going to notice why in the winter time now she starts up good but yeah i had the same problems too

i have a 90 daytona es 2.5l turbo just so you know

The TPS has nothing to do with the operation of the tranny.

I advanced the timing a little and now she runs better than ever! No more problems... YET!

Had to figure it out myself... thought I'd let you all know it's over, and thanks for the advice!

hey check for technical service bullitens i belive there is one for a rough idle when its cold, and i dont remeber but i belive it had in there that it a was when it was wet also, but check, if u get lucky and it is then you should be able to get it fixed for free