93 transport 3.8 acceleration problem

[danttusa]

I had to change the Computer Control Module last week. Since that time, when I accelerate from a stop the Van stays in first till the revs get extremely high then shifts. If I ease up on the gas when accelerating or accelerate slowly it will then shift to second just fine. I am also getting an error 13. I changed out the Ox sensor but it did not help. It is almost as if it thinks that I am going up a hill when I accelerate. Again, if I ease up on the gas and lightly accelerate I have no problem.

[LMP]

What were the symptoms in the first place that lead to replacing the computer....and where does the replacement computer come from? Sure it comes from same model year? '92 (no EGR) does not fit '93 (digital EGR) does not fit '94/'95 (linear EGR)...If something weirder happens AFTER changing a component, I suspect the new component, or that some connection was lost or forgotten in the process. SO before looking for something ELSE, I thing necessary to return to square 1......sadly.

[danttusa]

This Van goes through Computers every 4 to 5 years.
The original problem was the Van Bucking when accelerating. It was like driving a 5 speed Manual transmission and not knowing how to drive a manual. The replacement computer fixed that problem. Yesterday, I got another replacement computer, just in case that replacement was bad. Symptoms didn't change. The computer came from Advance Auto parts and was identical PN etc to the one that I had to replace initially.
Van idles good, drive great but only has a problem when in first andaccelerating. It works fine if accelerating very slowly. What I am doing for the present time is accelerating, getting to about 15-20 mph, take my foot off the gas entirely, then when I accelerate again it shifts to 2cnd. Works everytime!

[LMP]

Is Check Engine Light ON?....I'd be tempted to check the throttle position sensor, and see if you can read a continuously increasing voltage at pin 2 or B when slowly depressing the throttle.
www.avigex.ca/xport/tps.jpg
www.avigex.ca/xport/tpsloc.jpg
The original symptoms are very much like those occuring with a broken TPS...and may be the new computer has not had the "learn" time long enough to adapt to faulyt condition and delivers different symptoms for same problem....
A problem with the transmission could also be the basic cause....In case you have the CEL ON, use this to pull the codes:
www.avigex.ca/xport/readingdiagnostics.jpg

[danttusa]

Sorry my response has been slow. My Ford also had problems which I had to fix first. The 93 transport still has the shift problem but now is getting DTC 56 = Quad-Driver QDM "B" circuit. On www.avigex.ca/xport/3800codes.jpg referenced the appropraite code. Page one states to go to page 3 for to isolate but there is no page 3. I can't find any info on this error to help me further troubleshoot. Any help would be appreciated. Thnx

[maxwedge]

Certain solenoids are driven by quad driver B in the pcm, not sure which one, you will need a comprehensive wiring daigram for that but one of them is overloading the circuit causing the code, egr solenoid, tcc solenoid, evap solenoid are some possibilities.

[LMP]

OK from www.avigex.ca/xport/dtc56.jpg that you quoted, you ee that this linked to solenoids A and B that control gear changes.
Here are the other pages of that topic,
www.avigex.ca/xport/dtc56_2.jpg
www.avigex.ca/xport/dtc56_3.jpg
These are designed to test the output of the quad driver - by the way the output transistors can be replaced..
but basically, you should check first for continuity of solenoids cicuits at the plug
www.avigex.ca/xport/tccloc.jpg
www.avigex.ca/xport/transaxleconnector.jpg
each solenoid has the 2 wires fed through that plug E being the common. Measure between E and B, E and G, F and B and each should read about 20 ohms.
THen if proven OK, I'd connect the plug AND check the same but from the main engine harness connector at the PCM plug...to make sure straight copper wires DO conduct electricity...which is not to be taken as granted as dramatically demonstrated recently by Canaris....

[danttusa]

Thanks for the missing pages...believe me your help is appreciated!! Now I have to ask the question...where is the quad driver located? I had gone to a parts store and they didn't know and I couldn't find it in the manuals they sold. I have the meters etc to check the output transistors, continuity, etc but need a description of where I can find it. Thnx again for your help!

[LMP]

Well a forum member from UK if I remember well did replace driver transistors...was it Paul Taylor or KingArthur??.I'll check that out ....but these drivers are part of the ECM....

..yeah here it is: check this Paul Taylor's thread:
http://www.automotiveforums.com/vbul...d.php?t=507692

I can email you some info on that code. Yes it is in the PCM.
I am scrapping a 93...has new PCM just before I parked it...
Chaeck your grounds...they really play on the voltages that drive the PCM crazy...unfortunately grounds are all over the place...again, I can email to you if you'd like.
Paul

[danttusa]

Thanks for the info on grounds. Since the van came from the NE and has much rust...it is something I will check out. This Van has had electrical problems since it was new. The dealer had to change out one of the harnesses way back when. I have a new issue maybe someone can help with. Does anyone know what size serpintine belt is necessary for the 3.8L so the AC can be bypassed. It shows the routing of this belt but I can find no PN or size.

[LMP]

Yes I have one. The best size is 72 1/2 inches....multiply by 2.54 for cm if needed, .....but mine is 72 inches and that is OK, although the bender is cranked a little farther

EDIT : ....mmmm...at least that is what I though remembering, memory is a tricky accessory...so disregard the above.
...... I have the belt in my hands now : it is a DAYCO 5060710.....and 710 means 71 inches...which means the best would be 71 1/2 inches, ..well may be 72 WAS to be the right size after all...(I"m beginning to loose trust in what I remember....)
Mine is exactly like yours, a '93 3.8. WHen I bought the belt , the exact size was twice the price ...no explanation...so I took the somewhat shorter one knowing it could be handled.

I also checked at ROckAuto.com for car models using similar engine but listed without the AC and the belt sizes shown vary between 72 and 73.5 inches....but there may be slight variations in power steering and altrernator position and other accessories for other models (oldsmobile ROyale of late '80 vintage)...

[danttusa]

Had the transmission changed. They found that one of the selonoids was fried along with some other problems. The vehicle now shifts fine but has a hesitation when starting from stop. It acts as if it is gas starved. They suggested a fuel injector cleaner since they ran the car on basically fumes by the time I picked it up.
Also, the shifting indicator is no longer present, so there is no visual to what gear I have selected. Does anyone have the procedure for rplacing the indicator and GM part number? Again it is for a '93 transport, 3.8l w/ overdrive. Thanks. At least the vehicle is drivable again!!

[LMP]

THe shift indicator is a string attached between the needle and the steering column..nothing technical. Just clip it at the right place so it indicates properly, a trial and error procedure.