Author Topic: Vehicle problem, need advice. (Read 3194 times)

Felonious Monk/Fignozzle · « **on:** May 20, 2006, 08:54:46 AM »

I have a 1998 Grand Caravan with 120,000 miles on it. This was purchased used a couple of years back, and has been utilitarian until now.

Here's the problem: At a stoplight, the RPM's jump, revs and almost dies. It also gets hot and goes into the red. On the highway, it acts like it's missing, but runs. The Mayberry mechanic (an independent, but otherwise competent and has a lifetime of experience, and nice guy) has had the van for a month; he has found and patched 2 leaks in the manifold; did a tune-up, changed the fuel filter, and the problem persists. Sounds to me like a timing belt problem? But I am very mechanically challenged, and so my opinion is pretty much worthless.

The van has sat in the back of his shop untouched for two weeks, and he made the statement to my wife that he needed to set it aside and come back to it because he doesn't know what to do with it.

I've currently paid him for a tune-up, patching the manifold leaks, and we're sort of at a standstill.
The plan is to just get this fixed enough to sell, so I can take what we get out of it and buy an new(er) van.

How would you proceed? Anybody know what's causing the mechanical problem?

K Frame · « **Reply #1 on:** May 20, 2006, 09:03:14 AM »

I sincerely doubt if the problems you're describing are a timing belt issue. I'm pretty sure that that engine is an interference engine. If you have a timing belt problem, you would have pistons ramming into valves.

Getting hot and running into the red could be many things, from a collapsing hose to a bad fan clutch to a bad thermostat.

The other problems? Could be a vacuum problem. Inspect the vacuum hoses. I've seen a couple cause very weird problems when they get old and collapse when trying to pull a vacuum.

280plus · « **Reply #2 on:** May 20, 2006, 10:21:27 AM »

My old plymouth was doing the almost dies at stop lights and it turned out to be the EGR valve (whatever that is) But +1 on the vacuum too. the overheating part strikes me as funny. Maybe it's acting up cause it's running too hot? Just a guess...

mfree · « **Reply #3 on:** May 20, 2006, 11:05:23 AM »

Has anyone pulled the computer codes?

280plus · « **Reply #4 on:** May 20, 2006, 11:20:00 AM »

Gee, that's kind of a personal question, don't you think? Tongue

Monkeyleg · « **Reply #5 on:** May 20, 2006, 12:20:15 PM »

Keep in mind there's also a lot of black boxes that control idle speed, mixture, etc.

I had a similar problem with my 1991 Saturn--high revs, etc. The mechanic did what he could to adjust the carb linkage and settings, but it was still revving too high. Then one day the problem just disappeared.

Parker Dean · « **Reply #6 on:** May 20, 2006, 12:44:04 PM »

Sorry to say, but it's time to pull the vehicle from that shop. He may be a nice guy and all that, but he's obviously ill informed regarding the operation of computer controlled vehicles. Plus, he's effectively telling you, without saying so directly, that he'd rather you took it somewhere else because he hasn't a clue where to go from here. He'll probably be a bit relieved if the vehicle did leave.

The symptoms descruibed sound like at least two issues. The surging idle could be low idle speed due to carbon build up on/in the throttle plate/pcv system, or a stuckopen EGR, or a....

The overheating could be the cooling fans not coming on, or a clogged radiator, or a stuck thermostat, or a...

My point is that there are so many things that could be wrong based on the info provided it just isn't feasible to come up with a course of action beyond taking the vehicle to a shop known for driveability diagnostics.

garyk/nm · « **Reply #7 on:** May 20, 2006, 12:49:38 PM »

Do the revs go crazy while the AC is running? If so, it might be the idle compensator gone kaflooie. Had that happen on a Lebaron.

Marnoot · « **Reply #8 on:** May 20, 2006, 01:17:22 PM »

Similar symptoms in my car have been indicative of a bad MAF (Meter, Air Flow / Mass Air Flow sensor) in the past (the revving and almost-dying at idle that is, not the overheating). Of course my car is a Maxima, so I have no idea if similar problems would be caused by that component in yours. Just another idea on the heap for you.

Azrael256 · « **Reply #9 on:** May 20, 2006, 01:43:37 PM »

Quote

The surging idle could be low idle speed due to carbon build up on/in the throttle plate/pcv system, or a stuckopen EGR

Second on the EGR. Second on the Airflow. Check the idle air controller.

InfidelSerf · « **Reply #10 on:** May 20, 2006, 03:15:27 PM »

Quote

EGR valve (whatever that is)

Exaust Gas Return
Once plugged up with carbon deposits it can certainly cause poor idling and surging.

Another itme to check out is the oxygen sensor, they give vital information to the computer. When they aren't functioning they can cause many of the symptoms you describe.

Just out of curiosity what did that mechanic charge you for the stated repairs?

Felonious Monk/Fignozzle · « **Reply #11 on:** May 20, 2006, 05:45:06 PM »

Thanks, guys.

Quote from: veloce851

Quote

EGR valve (whatever that is)

Exaust Gas Return
Once plugged up with carbon deposits it can certainly cause poor idling and surging.

Another itme to check out is the oxygen sensor, they give vital information to the computer. When they aren't functioning they can cause many of the symptoms you describe.

Just out of curiosity what did that mechanic charge you for the stated repairs?

$139 and change so far. Not terrible, IMO.

InfidelSerf · « **Reply #12 on:** May 20, 2006, 07:01:34 PM »

no not bad at all. I would say that removes the question of him taking advantage of you.

Werewolf · « **Reply #13 on:** May 21, 2006, 05:31:17 AM »

Almost the same thing on my Camaro. The main problem was (best I can explain) half of the computer was dead. Replaced same and had dealer program - end of problem.

Have a dealer check your car - not some independent. Modern cars are highly technical and dependent on their computers. Dealers have ALL the stuff needed to check them (some of which is proprietary) and no matter how good an independent is he still doesn't have access to the same level of training and equipment that the dealer does.

I know dealers charge exhorbitant rates but sometimes they're one's only choice.

280plus · « **Reply #14 on:** May 21, 2006, 05:49:39 AM »

I agree with werewolf on the dealer thing but just want to mention, having a brother who's been a mechanic for Ford for over 20 years, I know that because things have been slow recently dealers have been letting their key people go keeping only one or two, and hiring noobs fresh out of tech school to replace them with. Look around their shop. If you see a bunch of very young looking guys walking around chances are the "cost cutting measures" are in effect. This also leads to the one or two experienced guys being burnt out and PO'd cause they're constantly fixing the noobie screw ups and not making "incentive". Believe me, I get an earful every time I see him. shocked

Monkeyleg · « **Reply #15 on:** May 21, 2006, 01:01:38 PM »

The EGR valve is just a politically correct crankcase breather.

Don't know about EGR valves on later model cars, but if I had one go on 80's vintage cars I'd just pull the valve off and plug the fitting on the carbeurator.

Drove the dealer mechanics nuts.

InfidelSerf · « **Reply #16 on:** May 21, 2006, 07:15:59 PM »

Quote

The EGR valve is just a politically correct crankcase breather.

Yep part of the whole emissions control system.

We would do the same thing with EGRs on 22R toyota motors too.
Actually there is alot of crap you can remove due to emissionss control stuff.

My idea of a good emissions control system is called a turbo

Sylvilagus Aquaticus · « **Reply #17 on:** May 21, 2006, 07:43:50 PM »

I'd go over the thing very carefully for vacuum leaks. The surging/struggling at idle sounds like either one whopper of a vacuum leak or the Mass Airflow Sensor is dead/dying, especially since you state it 'acts like it's missing but it runs' at highway speeds.

As it's a 1998 model, it'll have the OBD II readout connection. Get someone who can run the codes. A vacuum leak won't necessarily show up, but the MAF and any other sensors/regulators most assuredly will. From those, a good diagnostician can spot a possible vacuum leak. It may even be a computer-controlled ignition timing problem, too.

Regards,
Rabbit.

S_O_Laban · « **Reply #18 on:** May 21, 2006, 07:58:07 PM »

Actually the symtoms you describe would cause me to check for a blown head gasket. Something many of those vans where noted for. ( I made a bucketfull of money off Chrysler Minivans in a former life.

)

The key thing to fix anything is to start by checking the basics. Which includes compression, timing, fuel and spark.

Plus one on letting another mechanic take a look. Who ever said your mechanic will be glad to see it go, is exactly right.

280plus · « **Reply #19 on:** May 22, 2006, 12:48:05 AM »

Just to reiterate, not idling when stopped and running OK on the highway except for "missing" (sometimes it would other times you'd think it was just fine) still sounds EXACTLY like what mine was doing before they changed the EGR. First I changec the fuel filter and when that didn't work I thought I would have to look for a vacuum leak myself because it DID kind of mimic that, but not so as it turned out.

richyoung · « **Reply #20 on:** May 22, 2006, 04:52:51 AM »

Shot in the dark - cooling fans not comming on, collapsing hose, or bad thermostat - this could explain ythe overheating, AND the bad idle, IF the A/C was on, as the compressor would be fighting to compress refrigerant that wasn't cooled in the condensor by airflow. The occasional miss at highway speeds could be due to glazed plugs or damadged wires from over-temp.

mfree · « **Reply #21 on:** May 22, 2006, 06:07:16 AM »

*ahem* has anyone pulled the computer codes?

You know, the computer will tell you if it can't properly control the EGR valve or the AIS motor/bypass, if there are lean/rich issues (indicative of a bad O2 sensor which can cause idle problems), etc. etc.

Pulling codes on a modern car is like reading plugs on an older one, it's step number frickin ONE. I know the voodoo that's an older vehicle, I've set dwell on a single point dizzy before and tuned idle mixture screws till my fingers bled, and I've also put together replacement ECU kits and spent many weekends diagnosing ford EEC-IV and Chrysler SMEC/SBEC issues, when I say pull codes, trust me, they're helpful. Then post them here.

About EGR being a politically correct crankcase breather: Negative. It's exhaust gasses rediverted to reduce NOx emissions when cruising. Blocking the EGR port will result in a lean condition, could even result in toasted valve seats eventually, though most modern engines' seats may as well be made out of tungsten, they're *tough*.

I don't know when chrysler switched systems but it may be as easy for you as sitting in the car and switching the ignition on-off-on-off-on, and counting the flashes on the engine light.

mtnbkr · « **Reply #22 on:** May 22, 2006, 06:28:39 AM »

If you have an Autozone nearby, they'll read the codes for free.

Chris

Felonious Monk/Fignozzle · « **Reply #23 on:** May 23, 2006, 08:53:21 AM »

Wow! Thanks to all who've weighed in with advice and options. I'll pick it up and see if my AutoZone will read the codes, and maybe by posting here we can narrow it down. Again, I'm just wanting to get this functional and sell it, so the least hit I can take $$$ - wise is best.
To Be Continued...

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Author Topic: Vehicle problem, need advice. (Read 3194 times)

Felonious Monk/Fignozzle

Felonious Monk/Fignozzle

Felonious Monk/Fignozzle