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Few more problems with 3.5L

2K views 27 replies 8 participants last post by  Kevin abq 
#1 ·
The last few days I've been having a problem starting my car, cold in the morning. It won't start, I crank it for a long time, wait a few seconds, crank again. NO luck. Then if I floor the gas about 1/4 the way and crank it, it starts. Then after I drove it, going up a hill it was misfiring and bogging and crapping out. I touched the gas a bit and it felt like stumbling. Then after I coasted down the hill and the car warmed up some more, it went back to normal. What could be wrong? I'm suspecting something with the intank fuel pump or the Throttle Position Sensor. Everything in the car has been changed recently, sparkplugs, PCV, oil & filter, sparkplug wires, fuel filter, MAP sensor....so it can't be those things.:rolleyes:
 
#3 ·
My diagnosis? Your plugs. I know they're new, but there's a TSB on it somewhere that all 1st gen 3.5Ls should switch to Champion copper plugs gapped at .035".

Ah, here it is, TSB 18-15-95, Engine fails to start in extremely cold weather (below 0°F.).

"Champion RC-12-LYC gapped at .035" is the only sparkplug certified for the 3.5L" And, "a PCM software update is required as well for vehicles manufactured before Feb 17, 1995" in order to maximize use of these plugs and improve cold weather starting.

fyi, the mopar P/N for these plugs is 56027275

HTH
 
#5 · (Edited)
Thanks for the suggestions guys. Right now its a Pain the Ass starting the car cold. It wont' start at all. I have to give it some gas and try a few times, before it will finally idle. Even then, I have to rev it up to about 2500rpm to keep it alive. I am currently using NGK G-power platinum plugs gapped at .050mm cause that's what it said in the owner's manual. I see you guys say .035mm? how come that low??? I do hope to god that its the spark plugs somehow....cause if it is indeed the crank position sensor, aren't those things very expensive and labor intensive to change?:(
 
#6 ·
It’s true if your crank or cam sensors are faulty your car won’t start correctly if at all. But, typically those particular sensors will set a code and flash your check engine light if a signal isn’t present.

Btw, the gap change on 3.5L plugs from .050 to .035 happened a few years back after many folks were having cold start problems on early model 1st gens. Like I mentioned though, I believe a PCM flash is required in conjunction with the switch to the .035 gap. This evidently cures the cold start problem. I remember another member here, FredB, said the plug change fixed his cold start problems.
 
#7 ·
It sure did! The TSB is #18-15-95. You need Champion type RC12LYC plugs gapped at .035" and a PCM update. This will cost about an hr. labor or so and if you have it done get the TCM updated at the same time. Will improve the tranny shifting. TSB also wants 5W-30 oil in the winter but not in the summer. Might damage engine????

FredB

FredB
 
#8 ·
What happens if I get those Champion plugs gapped @ .035" and NOT do the PCM update quite yet?
 
#9 ·
roshg said:
What happens if I get those Champion plugs gapped @ .035" and NOT do the PCM update quite yet?
Give it a try and see what you think. I don't think it would matter for a short while. In fact, my guess would be you'll see immediate improvement. I suppose in the long run though, it may not be good for the coil pack depending on how the PCM is communicating with it, i.e. peak load current tolerances.
 
#10 ·
Ok I did the gap adjustment, BUT its still won't start. It takes about 5 mins of struggling and me giving it gas. When it warms up, it is back to normal idling, but it still misfires high rpms. So now I'm thinking its gotta be a SENSOR. Which sensor should I check? I'm thinking of buying a Haynes manual on the car, and doing some voltage/resistant checks on some sensors. I'm suspecting the Throttle Position Sensor or Cam Position Sensor
 
#12 ·
thanks Fred...I want to do that...so do I need some special code checker to do this?
 
#13 ·
#14 ·
Is it possible that you have a bad or dirty injector(s)? Also could be the TPS. It's something definately in the fuel delivery system. I would check the TPS....sounds like the symptoms of a malfunctioning one. You will need a voltmeter to do it though...Got one? Otherwise if it's not to exspensive, just replace the dang thing. As a rule of thumb, always start checking the simple stuff first.....
 
#15 ·
I'm still putting money on the platinum plugs. Even when mine were gapped at .035, my car idled like ass. I switched to copper and my trouble went away. I never had the "cold" start prob though (S. Texas resident here :p ).
 
#16 ·
I have been having the same problem with a 96 with a 3.5.
To get it to start i would disconect the coolant temp. sensor
located right beside the thermostat housing and the intake
air temp. sensor located under the black 3.5L cover.
I would then put the accelerator to the floor and it would start
all most normally. Then plug in the sensors again.
First I replaced the coolant temp. sensor
no change, tonight I replaced the air temp. sensor.
I will know more in the morning.
 
#17 ·
Holy, really argus? OK thanks for the tip man! Cause yeah, I just simply regapped my NGK Platinum Plugs to .035. Well, its worth the switch to the Champion coppers since its inexpensive. Hope that cures this problem.

Cobra65...Thanks for the advice! I am concerned about my TPS, since I do get a lot of missing and hesitations at the higher rpms still. I have a voltmeter at home and so I'll check that and see what I get. I use to have a Turbo RX7 before, and I know it accelerated like crap and idle weird when the TPS went bad, and after replacing it, everything was back to normal again. So lemme do some investigation in that area...
 
#18 ·
roshg said:
Well, its worth the switch to the Champion coppers since its inexpensive. Hope that cures this problem.
It's worth a try to switch to coppers, but you may not realize the full benefits of the smaller gapped copper plugs until you get the PCM update. Btw, did you come up with any diagnostic codes on the check engine light?
 
#19 ·
Not yet argus, I read in the Haynes manual of some procedure using the keys and flashes of the check engine light...sounds complicated, but I will do that over the weekend and see what it says.
 
#20 ·
Well good news, car started fine today,
with the new sensors.
Guys you can play with the plugs all you want but if the ecm
dosn't know it is cold it will not adjust the timing or the fuel.
just my opinion.
autozone coolant tepm. # su326 $13.99
air temp. # su343 $19.99
not su325 like there computer says
crossed the # off the original one
and it looked nasty when I took it out
it probable couldn't read any thing.
 
#21 ·
Ok guys, the saga continues. Geez, haven't been able to drive the car for a few days now.

Ok, so I switched to the Champion Coppers today as recommended by you guys, gapped at .035mm. The car still doesn't start normally. So I unplugged the battery for about 15mins, and plugged it back in. Still doesn't start.

What happens, is it turns over, starts for a second, then dies...I keep trying and trying, sometimes it will run for 2-3 second, then die again. So I unplugged the coolant temperature sensor while it was running and wanting to die, and the FAN came on right away. Right afterwards, I plugged the sensor back in and then the car finally IDLED properly on its own, and didn't die. Dunno if by doing this I richened or leaned out the mixture. Anyways, right after this, I performed the diagnostic code retrieval procedure and this is what I got:

Code 12 - Problem /w the battery connecction. Direct battery input to controller disconnected within the last 50 ignition key-on cylces (proly because I unplugged the BATTERY!)

Code 13 - Indicates a problem with the MAP sensor pneumatic (vacuum system)

Code 14 - MAP sensor voltage too low or too high

Code 22 - Coolant sensor voltage too high or twoo low. Test coolant temperature sensor. (dunno if this is related to me unplugging it while the car was idling??)

Code 55 - Completion of Fault code displays by check engine light

Now I'm thinking about the MAP sensor could be faulty, but I just pulled the file on my car's history from the previous owner, and he had replaced the MAP sensor back in October 2002! Dunno why he did that...but I'm wondering if it can go bad that fast?

Ok, any suggestions guys? :-(
 
#22 ·
roshg said:
Now I'm thinking about the MAP sensor could be faulty, but I just pulled the file on my car's history from the previous owner, and he had replaced the MAP sensor back in October 2002! Dunno why he did that...but I'm wondering if it can go bad that fast?
Maybe it isn't bad. It sounds to me like it isn't even connected. Did you check the electrical connection at the map sensor?

The MAP sensor is the one screwed in to the driver's side of the intake plenum. Make sure that its connector is attached firmly and in good shape. You may want to disconnect the connector to look at the plug contacts and make sure they aren't bent or corroded too. A MAP sensor will run you $70 bucks or so, so I'd rule out the easy stuff first (bad connection), before I'd spend that kind of money.
 
#23 ·
I had the exaxt same problem you described, exactly. It ended up being the intake gasket, when trying to start the car on cold mornings the engin was getting too much air and you had to give it a lot of gas to get tit to start and then the car would try to bog down and stall at idle, unless I kept my foot on the gas. the dealership replaced that gasket and I got them to replace the plugs also and now my car is fine.
 
#24 ·
I'm pretty handy with tools amd mechanics....is the procedure to changing that gasket fairly straight forward? Seems like all you gotta do is disconnect the air intake tubing, and remove a bunch of connections and then unbolt the intake manifold?
 
#25 ·
Ok guys, PROBLEM FINALLY FIXED!!!!! I'm sooo excited! Well, I guess the computer was right...it was saying something is wrong with the MAP sensor, which was true. I was suspecting the intake manifold gasket as you guys had mentioned...so I sprayed some carb cleaner around the no6 cylinder...and I started the car. It still idled roughly...then I accidently bumped the MAP sensor by accident with my hand, the car stalled. I was like WTF?!...so I checked to see if the connector was on properly which it was. Then I noticed, hey I can spin this MAP sensor around freely with my pinky...WTF?!.... Ended up that when whoever did the replacement of this thing, never tightened it !!!!!!!!!! It was just on there LOOSE and proly creating a huge vacuum leak!!! So I tightened it onto the intake manifold and restarted the car, and it idled PERFECTLY. I was first skeptical about it, so I wanted to go up a steep hill and see if the car would hestitate, buck and crap out like it always did since the day I bought it...and man oh man, it seem like it had gained a solid 30HP!!! it revved and pulled to redline soo freely, I was like WHOA! So I finally traced the problem to a huge vacuum leak from a MAP sensor that was poorly installed. Now the car is perfect. I was just wondering one thing though, I replaced the sparkplugs to champions with .035mm gap, when it wasn't really necessary...I doubt the NGK platinums gapped at .050mm gap did any harm...so I was thinking if i should regap the champions to .050mm since I haven't done the PCM update yet?
 
#26 ·
Oh yeah, I forgot one most important thing. Thank you guys soooo much for all your help and advice. I greatly appreciate it, you guys are the BEST!
 
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