1995 3.5l Intrepid Idling Problem [Archive] - DodgeIntrepid.Net Forums - Dodge Intrepid, Concorde, 300m and Eagle Vision chat

: 1995 3.5l Intrepid Idling Problem

02-04-2008, 11:00 PM

Little background information before i explain the problem..

Year: 1995
Engine: 3.5l?
Miles: 102k
New transmission: 3-4 years old ( Only major work its ever had )

Problem summary:

Problem started around 3 or so years ago and it mostly happens in the winter time..

Some times when you first start the car after about 12-24 hours of it sitting it will start normal but the rpm will just drop and it will die..

Most times after that you cant get it to start again unless you hold the peddle to the floor and crank over the starter and then it will turn over and you have to keep your foot on the peddle holding the rpm at about 1k for 5 minutes..

After 5 minutes it is fine and idles on its own

This problem only happens every so often but the next problem ill explain seems to be linked to this problem.

Problem 2 Summary:

When driving if you let off the gas to slow down for a stop sign or whatever it might be you let off the gas for the RPMs will drop under 1k down to probably 1/2 grand some times all the way making the car totally stall..

When the RPMs go down the lights and everything fade..

I am guessing the 2 problems are linked together as they are pretty much alike..

I am hoping someone can give me some insight on what might be the problem

I dont want to have to take it to a mechanic without trying to find out whats wrong with it myself..

I might post a video of it happening to give a idea to the members what exactly is happening but its pretty self explanatory, RPM fades down some times to total engine stall.


Questions if i didnt explain myself good :)

02-04-2008, 11:54 PM
1) Upper & lower intake manifold gaskets.

2) Champion factory spec copper spark plugs + new plug wires if they haven't been replaced in a while.

3) Check for codes; things like oxygen sensors can contribute to this set of symptoms. But if you do items 1 and 2 above the two problems you've listed will very likely be solved.

02-05-2008, 12:00 AM
1) Upper & lower intake manifold gaskets.

2) Champion factory spec copper spark plugs + new plug wires if they haven't been replaced in a while.

3) Check for codes; things like oxygen sensors can contribute to this set of symptoms. But if you do items 1 and 2 above the two problems you've listed will very likely be solved.

I have done #3 no codes just the normal End Codes, code 55 i think it is..

Are the intake gaskets hard to replace?

Also if the plugs or wires were bad wouldnt you hear it miss firing?

02-05-2008, 06:03 PM
Gaskets are not hugely difficult; "low to moderate intermediate" is probably how I'd rate them, kinda like how some of the tv shows rate difficulty. The whole gasket set is $6, maybe $7. A shop will charge several hundred to replace them; if you're slow like me you can do a gasket job in a day or two, provided you don't have to replace any broken bolts and stuff like that.

It will take longer if you've never pulled the intake plenum and other stuff off the top of the engine, because you'd want to make sure everything is marked and such. If you've done parts of the job before, it will go faster. The whole procedure is well documented in this forum. My experience is that the hardest part of the job is cleaning the head surfaces where the lower gaskets go -- you gotta get everything clean and at the same time keep stuff from falling into the engine.

Yes, truly bad plugs and/or wires would cause misfiring. But using other than factory spec copper plugs, and maybe in combination with older wires, can contribute to some documented "cold start" problems in 3.5s. IOW, it's only in cold weather that they just don't quite give you the best ooomph for starting.

There have been some TSBs put out concerning "cold start" issues; mostly they do make note of plugs and wires, and I think in one case it even mentions getting the computer reflashed with newer software. If you're looking to save some cash, do the gaskets first; the plugs and wires are much easier and can be done later if the gaskets don't fix everything.

Ironically, the "cold start" TSBs don't mention the intake gaskets -- but with my fleet of 3.5s, I can tell you that the gaskets made the biggest difference...

02-05-2008, 07:31 PM
Gaskets would make it lean misfire ALL the time at idle. Check/clean the IAC (idle air control). It is easy access, use carb cleaner on it, let it sit overnight with the cleaner soaking in it, rinse with brake and parts cleaner and reinstall it. If you have the money to spend simply replace it.

EDIT: I am from cold a weather area, Just how cold does it get in Missouri?

02-05-2008, 09:03 PM
Well, I'm planning on replacing my intake gaskets this weekend. I never had the plenum off before, but I practiced in my mind a few times. The rear cam covers o-rings also and a fuel injector, just in case. Hopefully the engine will be smooth idling after that.

By the way mine always idles at 600 RPM, occasionally 700 RPM.

02-06-2008, 12:38 AM
if i was to take it and have a mechanic shop run diagnostic would the idle problem show up on their machines?

02-07-2008, 12:01 AM
Riddler, I can't say if anything would show up on a shop's machines, but do keep in mind that your car's own computer is saying it doesn't know anything -- and it's getting a whole bunch of sensor inputs. Pretty often it will give you generic misfire codes which the manuals suggest are electrical in nature, but they rarely are.

As bigjim195944 says, look at the IAC as well. It can certainly play havoc with driveability... although problems with it will often set a code in the computer since that's one of the data inputs. Since the lower intake gaskets are downstream of all the usual sensors, problems there are very difficult for the computer to know what to do with. And I think it's reasonably safe to say that every 1st gen 3.5 will eventually require the gaskets to be replaced.

Actually the gaskets can and very often are intermittent problems until they finally decide to go out for good. They can deteriorate to the point where they cause all kinds of problems in "cold" weather (in my cases both engines started and ran fine above 32F, and were complete bitches to deal with below that) -- but if you get them started and warmed up a bit they will run fine. Apparently a little heat makes something expand enough to eliminate most or all of the leak. Or.... let's just say that's *one* of the scenarios that's fairly common to observe with the intake gaskets. One of mine was doing that all last winter, but as soon as the weather warmed up it ran fine until I finally got around to replacing the gaskets in November. Has performed flawlessly so far after that, down to 0F so far.

Climate in MO varies greatly; here in the middle in an average winter it probably gets to about -5F a couple of times, and single-digit lows are pretty common. It can get as low as -20F though. Then again, it was 76F a couple of days ago and I did all my car servicing shirtless...

02-07-2008, 10:51 PM
I'm jelous! I have been working upstate NY (Rochester), Ohio and PA this week. Starrted in an ice storm then heavy rain then ice again with a few inches of snow on my way to Ohio and to clear and chilly (30ish) for the ride to Williamsport PA. this evening. I'm done for the week once I get home around lunch Friday. I gotta get the car in the air this weekend to find an exhaust sounding rattle, damn annoying but not critical.

I was picking on your um, cold weather as I was pondering last winters rides with my Trep. Toronto so cold (-35f) I had to get a jump for the first time in 200,000 miles and driving from New Brunswick (Edmundston) to my home in Ma. during each of three major storms last winter! This year has been downright balmy in comparison.

02-07-2008, 11:32 PM
I'm curious. I plan on replacing my intake gaskets this weekend. I figured I would take some pictures in case I forget where something goes when I put everything back together.

When looking at the intake, I noticed it was shifted backwards relative to the attaching bolts. It looks like the bolt holes in the intake must be larger than the diameter of the bolts. Does it need to line up with the bolts and the heads or not?

02-07-2008, 11:33 PM
First thing to do is to clean the IAC, AND MAP sensor. I don't know what first gen does but the second gen traps oil in the intake manifold, which gets stuck to the map sensor/IAC/intake temperature sensor and cause all kinds of weird things.

My car did this not holding idle thing for a while until I cleanned the intake manifold/IAC/MAP sensor. Then when I started the car, I thought it died again but it was actually idling so soft that I couldn't hear it.

02-08-2008, 04:57 AM
When looking at the intake, I noticed it was shifted backwards relative to the attaching bolts. It looks like the bolt holes in the intake must be larger than the diameter of the bolts. Does it need to line up with the bolts and the heads or not?

I don't think I understand the question. Everything pretty much only bolts together one way; with the manifold off you can see that there's one or two holes that actually don't get used, but you can't mis-bolt on that account.

Maybe it looks weird because of the symmetry of the heads? They are actually identical castings, but rotated 180 from each other when mounted on the block. Some of the hardware in/on them is not identical from side to side, but the basic head assemblies definitely are. You're kind of looking at a mirror if observing from one side to the other.

As far as bolt sizes go, they are somewhat smaller than the holes in the manifold, because they go all the way through it and thread into the heads. That's part of why breaking one off (due to corrosion, usually) normally isn't a big deal. It becomes a headless stud and the manifold should lift off over it. Then it's sticking out where PB or Liquid Wrench can be sprayed down into the threads, and vise-grips can probably remove it.

02-08-2008, 08:24 PM
Well, I managed to get the intake off today and replaced the gaskets. I still need to replace the cam cover o-rings and put the plenum back on. Hopefully, it will still run after I'm done.

The lower intake gaskets came off pretty much intact. I only had to clean off the ATV sealant around the water passages and a little of the silver coating from the gasket. The water line that attaches to the back of the intake didn't have a gasket other than ATV sealant. I made a new gasket for it.

Since the car had that occasional misfire on cylinder 5, I replaced it's fuel injector and the other's o-rings. I had a hard time getting the fuel lines back in the fuel rails, but I think I eventually got them seated and clipped in properly. Hope I don't spring any leaks.

02-09-2008, 12:29 AM
Make *certain* your fuel rail quick-connects are securely locked. Loosen the little tiny bolt on the hold-down bracket, then pull firmly and verify that there is a little bit of play -- just enough to feel a hard stop on both pulling and pushing.

That little bracket can actually hold the assembly together so it *looks* ok and the engine runs and starts good, even if there's not a positive seal. The result can be a connection that runs for a while, then creates a massive gasoline spill. Relatively speaking, that is. I lost about 6 gallons in 1/2 mile at 30 mph, and it was pooling by the curb on a city street!

02-09-2008, 05:54 PM
Got everything back together this morning. After cranking it for a couple of seconds, it started right up. Runs smoother now.

I cleaned the IAC. The car idles at 600 RPM. Is that where it should be?

02-10-2008, 05:07 PM
As long as it's smooth, that sounds about right. Congratulations!

03-07-2008, 08:30 PM
Hi all...
Could someone tell me where to find the IAC and what do I clean it with? Anything I need to know before cleaning the IAC? I have the exact same problems as the original poster of this thread.