Highway 'hickups'

[BYTS]

Good day to all
After looking at many, I mean many threads, I must say this is an amazing place! Thank you for being here.
My problem is like a ghost, once and while have rough idle, completely loose spark and gas for a milisecond on the highways or in town, no matter what gear i'm in. Intermediate abs problems, RPM runs erratic or not at all. Scanner tells me the cam and crank sensors , both check out great in ohms and DCV. Cleared codes , van still does the 'hick ups' in any gear, but now without any codes! checked the complete wire harness for breaks or corrsion, nothing. The computer is fine (tried a good used, still same problem).Will do it at any ambient or engine temprature. Filters, plugs ,wires all new. Any suggestions, short of burning it?
thank you in advance BackYardTroubleShooter

[LMP]

WElcome...Obviously a loss of electrical power..not something you want around Winnipeg in winter....Hard to pinpoint and hints will come but since this is about a '97, I suggest you also conduct a search through the Venture and the Montana forums , just in case.

[rockwood84]

make sure the battery posts are clean and tight .

[LadyCammy]

I have a 91 Transport 3.1 that is doing the same thing. We have changed the cap, rotor, wires, and fuel filter. At first it was a loose connection on the cap so we changed that out. It worked for like 2 days. When it started again we changed the ignition coil. It didn't seem to help. After we changed everything that we could think of it still seems to be getting worse. Our battery connection is fine. I'm really getting sick of the jerking or as i call it Humping the Road. It's only when i'm pressing on the gas, but i can swear when i'm going down the road EVERYONE else can see my van just a jerking. Any other hints as to what it could be?

[pes1956]

I have a 1990 Trans sport with the 3.1 and am having simalar problems, the first time was on a trip and it just died going down the freeway, acted like vapor lock. There was alot of pressure when I removed the gas cap, so I loosened the gas cap and never had the problem the rest of the trip. Talked to a mechanic and was told it was the fuel pump, so I replaced it...seemed fine for a few months then it started acting like you described going up a hill. Seemed to do it when the fuel tank was below half.

[rockwood84]

back yard troubleshooter----- your problem sounds like the x24 crank sensor the one behind the harmonic balancer as for the rest what codes are coming up? there are may things that could cause the hiccups from a dirty iac valve to a backpressuring fuel pump.how much fuel pressure is the fuel pump holding? a fuelpump only pumping 20 pounds of pressure will cause this . the fuelpumps gm uses on these motors are not the best made as most were made in mexico and are 95% plastic.

[pes1956]

The 90 3.1 does not have a crank sensor....It still has a distributer in 90. Its not bringing up any codes.

[LMP]

THis pes1956 3.1 being a 17 year old car (going on 18), I would not be afraid to buy an ignition module

as this component is a risk at that age and was proven a culprit quite often.
Don't leave home without a spare...

[BYTS]

I've checked all wiring components, to no avail. i found 2 out of 5 grounds that needing cleaning. fixed those 2 ( body ground beside wiper motor and under the dash) all codes disappeared. test drove again, still has the ' hickups' at about 80k give or take 20k. rechecked with scanner... no codes ... no the RPM gauge does not work at all. yes could very well be the x24 crank sensor! but this will not show on the reader. and it should?? will be checking fuel pressure with the homemade gizmo, and checking the fuel pump ground.. there has also been a Command start that has been disabled on the van. removed fuses prior and worked fine for a while then back again the hickups arrived?!coudl there be a relation? more so with the ground features?
I also change the gas cap, it also work for a short period of time, just to make it worse a week later. The only connection i found between the crank and fuel sonsors (or systems) is in the wiring for each sensor.( sharing grounds)
could it also be the tcc module in the tranny? 80k is a good range for the overdrive feature?

[BYTS]

Just an update.. completely removed the inactive command start, wiring, brain, etc. found the command start pc board has water damage ( interesting ) disconnected the x24 and relearned the pcm.. the 'hickups' are gone for now( crossing my fingers ) in the spring I'll r+r the x24 and see if it will still act up. But for now, i can live with no RPM gauge. there are now 200km of testing now so far so good..
Since the x24 controls the RPM gauge, would the eratic needle going to the red line kick in the rev limiter to cause the hickups? I'm thinking this is what was happening
Thanks you all very much for the ideas--BYTS

[rockwood84]

that could be it

[BYTS]

The X24 was the problem! no 'hickups' after the disconnection. It must also control the rev limiter as well as the tach. thanks again.

[LMP]

Originally Posted by BYTS

.. completely removed the inactive command start, wiring, brain, etc. found the command start pc board has water damage ....disconnected the x24 ...the x24 was the problem

Glad you are OK....but for the record.. I understand the command start is a remote control start...right ? and if so, these devices more than occasionally are cause of havoc....
now...about x24....??? disconnected from the "command start"....but is it stil in the normal ECM circuit...I suppose....please clarify these two issues....

[BYTS]

There was alot of issues with the older command starts.
The command start is not connected in any direct way to the X24. Just to the DIS module ( X7), brake switch at the pedal, external temperature senor,starting system and door locks (at least that is what was on this one).
Yes, the X24 is now disconnected from the ecm. Now there is some idle issues that have to be worked out.. rev fluctuation.. but by relearning the ecm a few times, it seems to be a bit better. It is my understanding that the '97 3.4 edition motors are the only Transports with the X24, Good thing to. It is not that important to have 2 crank sensors...except with these models....