I agree it something affecting mulitple cylinders, but broken valve springs, not likely. questions come to mind, why always 4 & 7?

when you swapped the injectors, how did the tops look? did you flush the fuel rail? (should next time its off if you didnt).

did something happen to the motor and then it started with the miss or was it a gradual thing?

things that affect all cylinders...
coil, crank sensor, cam sensor, map sensor, fuel (lack of it).

did you put a light on those two plug wires? are they getting spark? (you mentioned new wires so it should be ok).

i had a valve seat go bad on the #8 cylinder which caused a huge miss... yanked the head, got it fixed and put it back on w/o any problems. this was before I found out about the head cracking and new what to look for

 

Steve,

Thanks for the detailed response. I'm giving you a detailed account of what occured yesterday so that you have all the info that I've got. If something isn't clear, just yell!

The tops of the injectors looked fine. Because of that, I didn't flush the fuel rail, but also because I had a hard time getting the injectors in and out. (Since it's a van, it's hard to work on.)

The performance of this van has been degrading for the past two months or so. The check engine light started coming on about 4 weeks ago. I got involved this past Sunday.

Even though it ran after I did the injector swap, and test drove the same as it had, things took a turn for the worse yesterday morning.

It started and ran okay for him yesterday morning, but then after he got back home from an errand, it refused to start. I came over, verified that he had a healthy spark. Then, I verified that #7 and #4 were getting spark. I also looked at the throttle position sensor, Map on the scan tool. They looked normal. I checked the ohms on the TPS, it starts out at ~500 ohms and goes to 3,500 ohms resistance with no breaks. (I don't remember the actual values, but they seemed reasonable.) I unplugged the map and plugged the vacuum line going to it, still no start. Then, I cleaned the throttle body and IAC motor pintle. Still won't quite start. If you put the peddle to the floor, it kind of runs for a split second, makes a loud moaning sound in the intake and quits. While the fuel pressure was 49.5 at all times Sunday, now the fuel pressure gauge needle shakes while cranking. I also noticed that the fuel pressure drops steadily as soon as you key off. (I don't know about Dodges, but Fords hold the fuel pressure when you key off. I'm not sure if this is a problem or not.)

All the plugs that I took out Sunday looked quite normal. I took the new plugs out yesterday, and now the newly installed plugs were all very black.

The only other thing that may help in diagnosing is that now it makes this distinct, throaty sound in the intake area when you try to start the engine.

No check engine light, no codes.

Best Regards,

Mike

 

the fuel pump has a built in check valve to keep the injector rail at 49 psi for a while (long while) so right off the bat, that check valve is bad. when you crank it the pressure should stay steady... it's telling me that the pump or regulator may have an issue.

how much does the fuel pressure drop when you crank it?

were the plugs gas fouled? can you get a pic to upload here of one? (done by clicking Post Reply and not fast reply, gives the option to upload a pic). could be the coil is dying... that would affect the whole motor.

Also, I assume the airhat is off when your trying to start it??? (helped a guy with a starting issue that had a plugged air filter, took it off and it fired right up).

some added info you may already know... the cam sensor is responsible for the injector timing and is located under the dist. cap. the crank sensor is responsible for the spark timing. it's located on the back of the block on the passenger side where it bolts up to the tranny.

edit: oh yeah, and one other thing.. just because the pressure is up @ 49 psi does not mean the volume is there to keep up with the engine demand. sounds to me like your fuel pump is the next place to look.

 

Steve,

The Dodges have a check valve also? That's what I thought, but being unfamiliar with Dodges I wasn't sure. I compared pressure drop situation on the van with his Jeep Cherokee. They both acted similarly, so I assumed that it was okay.

The fuel pressure needle just swung wildly. I would say that it was swinging between 35-50 psi while cranking.

The plugs were a kind of flat black color, so let's assume that it was carbon/fuel fouled.

I had the air cleaner on initially. Once I saw that the van doesn't use a MAF, I removed it to continue attempting to start the van. He had a brand new airfilter anyway.

Thanks for the tip on the cam sensor!

You are probably right about the pump. I'll look into it further. However when we were driving it on Sunday, it held 49.5 psi even while it was misfiring.

 

could the wiring have a problem to those cylinders? I dont recall the firing order, are those cylinders back to back in the firing order? with the pressure fluctuating the way you mention, it almost sounds like there is a stuck injector in the open position.

check that... that doesnt make sense, it would still start.

 

Steve,

It was a plugged cat. I'm not saying that he doesn't have other problems, but once the cat was replaced it started, idled, and ran fine.

Thanks!

Mike

 

Cool, glad to hear you found the problem... this is the 1st time I've heard of a plugged cat causing a no-start situation. anyways... [sm=icon_cheers.gif]

 

I am having the same problem with my 98 ram van 2500. Same misfire codes #4,#7, multiple misfire. Van idles a LITTLE rough (not to bad). The main thing I noticed while out on empty highway checking top end is that at 69 mph the throttle does not have any effect past the halfway point, it does work fine until I reach 69mph. I do know that the accelerator is working because if I push the accelerator past halfway point at 69mph the gas does disappear (it doesn't get used, but it disappears) I found this out yesterday on a road trip. I traveled 65 miles kept trying to get past 70mph used 1/2 a tank of gas. On the way home I stayed at 65 and used only an 1/8 of a tank to travel the same 65 miles in opposite direction. It's almost as if the van has a governor on it, but it ran fine 6 months ago. This all started 6 months ago I accredited it to bad gas, because it ran really bad on one tankfull, but after that tank was used I put what I know to be good gas (amoco silver) and it got better but this other problem persisted. The van has power (although only about 80% of what it had 6 months ago), passing gear does work and shift and all that but only until I reach 69mph. Could it be TPS, some sensor on tranny, main computer??? Also does anyone know if buying a non-dodge (after market computer) a good idea ( I heard dodge computers have to be installed and programmed by dodge, and after market versions don't)???? Van starts just fine.