Very frustrated about this start problem. A couple of months ago, the truck became hard to start the truck in the morning. Took2-3cranks on a dry morning and 3-7 on a wet cold morning.

Took it to Pep Boys and they did an engine diagnostic. Codes showed multiple misfires and misfire on cylinder #8 as well as "Engine is cold too long" and "No crank reference signal at pcm". So I had them change the crankshaft position sensor and thermostat. They also did a dry compression test with these results:
dry test:
Cylinder 1 - 125 psi, Cylinder 2 - 115 psi
Cylinder3 -140 psi, Cylinder4 - 150 psi
Cylinder5 -150 psi, Cylinder6 - 150 psi
Cylinder 7 - 150 psi, Cylinder 8 - 150 psi
wet test:
Cylinder 1 - 150 psi, Cylinder 2 - 155 psi, Cylinder 3 - 160 psi

Problem still there.

Took it to Dodge dealership. They said the fuel pump wasn't holding pressure, bad check valve. They replaced it and said the truck shows a code saying that the truck is running lean. The wanted to change the catalytic converter but I said not to. Picked up the truck and it is better, 1-2 cranks in the morning. But still not running well at first. Vibrating like it wants to stall and sometimes does. IAC sometimes catches it, sometimes doesn't. After first five minutes, it runs fine.

Last tune up was 5 months ago and I took it back for them to check their work. Replaced IAC 5 months ago as well.

Any ideas? Is the catalytic converter the problem or is there something else to check? Any help appreciated.

 

hmm, long and ugly story.
regarding dealer... so they said it was running lean, and proposed fixing that by changing the cat. unbelievable. i don't think your problem has anything to do with the cat since you say its runs pretty good once it warms up.

compression sounds ok. ckp changed so thats eliminated. thermostat may have been bad if it wasn't warming up at normal rate, but that has nothing to do with how it runs for the first 2-3 minutes.
is your check engine light on ? are there any stored codes ? if there are any codes those need to be read and considered. what year is your truck.
how did it run after the tuneup 5 months ago ?
and this started 2 months ago.

just guessing out load, in no particular order.
could need iac again, new one may have gone out.
might have vacuum leak, including plenum. dealer said it was running lean.
tps maybe, could be giving false signal telling iac to stay out of the way.
map sensor. doubt it.
ambient air sensor. doubt it.
o2 maybe.
tune up again maybe.
coil maybe.
i'm not sure what to recommend. if you happen to have a real good friend with a dodge you might swap parts one at a time to try to find the culprit.
if i had to guess one thing i'd say you may have a vacuum leak, creating a lean and engine 'shaking' condition.
this could be cruise, vac lines, 4wd, heat/ac controls, etc.

 

No other codes. When it does start, it sputters for awhile. When I give it some gas, the rpms go down. Sometimes it stalls at this point but if it doesn't, I let it run at idle until when I give it gas, the rpms go up. At that point, I start driving it.

When I start driving, I try to let the truck start rolling on its own before giving it gas. If I give it gas from a dead stop at first, the rpm will momentarily go down then jump up. Like at some point, the computer gets it and just takes off.

After 5 minutes of driving, everything is fine.

Go figure.

 

could this be a really messed up throttle position sensor (tps) not telling the pcm to tell the injectors to give it some gas ?

 

Have you put a vacuum gauge on it? With the stock manifold, tb and valvetrain, you should be sitting between 17-20 inches. You canalso diconnect and plug the accessory boss coming out of the manifold,and see if the reading goes up. A vacuum gauge is a relativelycheap diagnostic tool for what it can tell you.

http://www.therangerstation.com/Maga...acuumLeaks.htm

 

Well I did come poking around the hood yesterday and the only thing I found suspicious is that the ignition coil spark wire was not seated all the way down on the coil. I disconnected it and put some dielectric grease and tried to seat it down. It wouldn't seat all the way down. When I tried to start the truck, it was sputtering like before. Since then I pushed it down again and it did seat all they way and the truck started a lot stronger.

I'm going to keep my eye on it for the week and see what happens.