99 Dodge Caravan - P0132, P0138, P0172....

I have a 99 Dodge Caravan Sport van, 3.3 L about 80K miles and I can't seem to shake the O2 codes. The engine is definitely running rich.. it smells bad...! It idles very rich (rough) for about 2 mins when its restarted hot and then all of a sudden it revs up by itself and runs smooth idle. Occaisionally, (totally intermittant) on light acceleration, it suddenly dies as if no ignition or starved of fuel then picks up again...

I have measured the O2 sensors and they appear to be ok. They fluctuate around .3 - .9 volts isolated from the wiring harness. I've also isolated the EGR valve and it still loses power. I have replaced the spark plugs too.

Also, when I increase the rpm to 2000 the engine 'hunts' up and down with fixed throttle....

ANy ideas anyone??

when it dies out unplug the Map sesnor and see if it restarts, it sounds like the problem is becoming more prevelant since your last posts, can you watch the Map values change if you apply vaccum to the sensor.
Map sesnors used to be a common failure as well, not so much anymore but it's common for them to get water in the vaccum lines and throw the sensor out the same way the EGR modulators fail, how did you isolate the egr. Glad to hear from you, was wondering what became of your van

Good luck and keep me postted

Jeff

Thanks Jeff!
Yeah! I'm starting to get me head down into it now... the deeper I look the darker it gets..!

I isolated the EGR initially by removing the vacuum hose from the top metal diaphram port and connected a long piece of hose to it. I ran the engine at idle rpm and repeatedly sucked on the hose to simulate the vacuum from the EGR Control Valve. Each time I sucked on the hose the engine would die, or reduce rpm. When I stopped, the rpm returned.

I raced the engine in bursts to check for back pressure effect vacuum from the EGR Valve control at the output and felt vacuum on the burst.

I reconnected the EGR vacuum hose and this time removed the Duty Cycle Purge hose from the throttle body. Still no benefit...!

I'm going to test the MAP sensor as you said! Good idea. But shouldn't I see a code reflecting that..??

Not always, remember sensors often only give codes when they go open circuit or short circuit, most of the time open circuit sensor codes are wiring, not the sensor itself, the O2 is telling you the fuel mixture is off,
the O2s probably aren't your problem, they are doing there job, telling you something isn't right, what did the plugs look like when you removed them, were they dark and sooty, black in colour, smell gassy? look as well at the coolant sensor values when the vehicle is up to temperature
and try to get a reading from the TPS although not as common as the EGR or Map that could also give you the symptons you're experiencing,
You could try leaving the map sensor disconnectted and go for a drive and see what changes if anything. The way you isolatted the egr isn't really the best way because it doesn't account for the valve being stuck half open. You have to remove it and block the passageways off with a solid cardboard gasket. Yeah the valve is moving obviously because it will stall the engine at idle but if the valve is sticking on decel it will stall ut the engine. Sorry this one is stumping you but I'm pretty sure we can fix it!!!!, The Map sesnors used to act like that all the time in the older frt wheel drive cars like the acclaims, 5th avenues etc. They'd stall out like they had ran out of fuel but as soon as the Map sensor was disconnectted they'd start right back up. Kinda like the computer thinks you're driving around at high altitude and really you're at sea level or vice versa and it screw up the fuel mixture, spark timing everything. Just check for any vaccum leaks around the intake manifold and such and maybe clean the IAC pintle and throttle blade in the throttle body and rescan those things i suggestted and get back to me, As sick as it sounds I'm kinda enjoying this challenge

cheers and good luck

Kepp me postted

Jeff

Jeff!
When I removed the plugs, I felt I'd solved the problem! They were totally worn out with gaps double that of normal. They were wet, dark and one was totally sooted up. I replaced them and the engine seemed ok for a while then started dying again... same as before.

I'm going to try the MAP sensor as you said and the TPS....

The beat goes on..!

I don't encourage throwing parts at it, I'm just saying what I'd be looking at with the scanner if I had the vehicle in front of me.

Good luck with the Map, I got my fingers crossed

Good luck and keep me postted

Jeff

Well! We're hopefully well on the way to solve this problem.

With the MAP sensor connected, I measured the voltage at the next 'downstream' connector (after checking the continuity with each MAP pin isolated) and with the ignition "on" +5V, with the engine running at idle, +5V.... no change.

According to the Chilton Manual, that's not ok ... Right? Actually, I should've measure this voltage at the source (back of the plug) just in case there is a wiring problem.

While I was in there, I checked the ETC Sensor. Measured 15K Ohms cold and 5.6K Ohms warm (but not hot).

I'll check the TPS next....

Wouldn't it be better if I measured all these input signals at the PCM? That way I can work the problem back to the sensor - asuming its more likely a wiring issue.... ??? Problem is, I don't have a pinout for the PCM.

Thanks for your help Jeff!

the way I always check a map sensor is using a vaccum pump to apply vaccum to it and comparing it to the sensor value with the scanner, or watching a vacuum gauge hooked up to the engine and comparing the sensor readings on the scanner with the gauge. I not trying to tell you to throw parts at it but I think you'll over analyze it and chase your tail if all you have for trouble shooting tools is a vot meter, it can be done but without some feedback on what the sensors are reading on the scanner it's till pretty hit and miss and very labour intensive, I'd suggest trying another map sensor, even a used one or else apply vacuum to the map sensor you got and see what the voltages and or resistances do, I don't have the specs for that so and again the map sesnor is just a diaphragm so even if internally the circuit is complete it can still be inaccurate. Block off your egr with a cardboard gasket and see what the van does.
What are yous using to pull your codes, just a code reader or do you have something that will give you live data?

anyway good luck and keep me posttted

I'm cheering for you

Jeff

Thats a good point! I'll remove the sensor and apply vacuum to it externally. I have no vacuum gage or other similar equipment but I recently bought a Geniscan GS100 code reader from a co in Canada recenty. It only reads codes.

Do you think I should invest in a vacuum gage??

i think you should invest in a map sensor and or a vaccum gauge, vaccum pump, compression tester, fuel pressure gauge, Dvom, 4 channel lab scope, Scan tool and a rollaway tool chest to store everything in!!

Just kidding that's what I use

but seriously see about a used map sensor and weigh it against the price of a new one and the price of any other tools you might need to purchase to further diag this van. How's it run if the Map sensor is disconnectted?

Just to be sure all our bases are covered you don't have any blown fuses for the O2s, leak detection pump or anything else in the fuse panels do you? I have seen O2 sensors blow the heater circuit fuse and cause all kinds of codes. I was just going through some of your past posts trying to see if anything was missed and though I'd ask. It's hard sitting here trying to diag it sometimes when the vehicle isn't in front of me. There is so many steps that I do almost instinctively when I'm diagnosing something that I forget that people reading these posts don't always cover as many bases as I do out of habit. Just a thought

good luck and keep me postted

Jeff

intersting you mentioned the EVAP.! One of the error codes is P1495, and P1495.... Is that the EVAP Detection Pump solenoid?? How could that impact the proceedings? I removed the Duty Cycle Purge hose from the manifold and there was no difference. Is that related? According to the Vacuum circuit, its a static device.

I'm going to pull out the MAP sensor and test it externally as you said.

Thanks so much for your help. Appreciate it!

Peter

That should have read P1495 and P1494...

I tested the MAP sensor independently by removing it, applying heavy suction to the diaphram port but there was no change in voltage (5V) between the 2 pins above the ground pin measuring it right at the connector..

I tried to run the engine with it disconnected and it won't idle.

Until next time...

evap codes like the 2 you have for the leak detection pump etc won't shouldn't affect how the van runs. Try blocking off the Egr valve like we talked about

good luck

Jeff

I will block the EGR valve later this week. I tried a new MAP sensor and made no difference. I have discovered there is no ground on pin 3 (the lower pin of the 3) of the MAP sensor.

I'm going to fix this thing.... eventually! Great learning experience.