Need help backfiring continues

[Kidhauler]

I posted another topic about a back fire into the intake I thought that we had it beat but it is now worse than ever. I need the van to get to work next week and the way it is it is undriveable.

I have changed the MAF,TPS, O2,and the oil pressure sensor. I put a rebuild kit into the TBI as it was looking kind of gross the pressure regulator baffle was disgusting. Sanj and I adjusted the shift points so it revved up slightly more in each gear to help it breath easier as it seemed to be short shifting it was in OD with the convertor locked at 60kph. It all seemed fine and ran well for 3 test drives. We then swapped out the gauge cluster for a newer one and took it for another test drive to check the speedo. About half way thru the drive the van started to run rough again. I took it home and parked it since I had to change the dash back as the speedo was way out of wack. I swapped the dash back and took it out tonight for a drive it is now backfiring constanly at any amount of acceleration. It starts at 40kph and everytime you touch the gas it backfires. I have hit the end of my rope I am going to change the plugs and leads and if that doesn't fix it I don't know what to try next I might just have it towed and crushed which would be a shame but I can't just keep pouring hundreds of dollars into the van and it still isn't driveable.

Has anyone had a simular problem like this on their van??? I am going to the pick a part on Saturday and might grab a distributor if they are cheap enough and I can find a good one.

[reaper]

"It's doin' it again"..............
Kevin,drop in some new plugs & leads & it should make a big difference.
I recalled you mentioning the nice Jolt you recieved from the wires when you
had your hand flat on top of the dizzy.I'll be around this weekend so let's kick
the crap out of it & get er fixed.

[Bikehauler]

I think we really need to check the timing on this thing. It must be sparking with a valve open. A really worn distributor could do this. When we unplug the brown wire if the timing moves we know we have a problem with the distributor. Also if it backfires with the timing set to a constant I would guess it's a cam problem. Either way let's have a look at it tomorrow night.
Rocke

[peter]

I'm sure that in the end, it'll be something stupid. Almost always is. If it was the dissy, it don't make sense why it'd run ok for a while, then start to backfire again. And you definitley shouldn't be getting shocked simply by touching dry ign. wires.
Good luck, bud

[BLAZER]

With the engine cover off, fire it up in the dark and watch the plug wire and the coil. you will see any arching in the plug wires in the dark. Also, lokk at coil. If it shows a blueish glow from anywhere, it's going out, needs replaced. I think it's in the distrubuter, sounds like the timing is moving or a lobe ot two on the cam is flattened.

[Kidhauler]

well here is the latest update. After what can only be considered the longest plug change in the history of man and all new leads I took the van for a run down the highway in the rain (worst case senerio) and she seemed to run fine with no backfires. I am holding out on calling it fixed just yet i want to run if for a couple of days to see how she goes. I have thought I had it fixed 2 other times and the problem came back after one day of good running.

I was looking on the AutoZone web site and they had a bad or malfunctioning EGR valve as a possible cause of backfires into the intake. So that is why I am holding out as that is the one thing I have not replaced yet. But so far so good. Thanks to those who posted replies and once again a big thanks to Sanj for coming over the other day and lending a hand. I still don't know the real reason he called that day.

[peter]

I think you're simply jinxed. Why don't you re-evaluate the use of public transport

[BLAZER]

I forgot about the plugs. I had a 76 chevy truck did the same thing, ended up like 3 plugs were fouled out, hardly firing.
Hope you got it done for good now!!!

[coolen]

hope you're makin' out well. if not, i second the idea of checking the timing


good luck

[Kidhauler]

Well I ran it on a 4 hour drive out to the Pick a part with Sanj and Stephanie and it ran well the whole way out. The idle was a little rought but if I turn it up about 100rpm it should smooth out as it idles better in park than when it is in gear. I had it running 120khp the whole way out and back and as well as driving it right in the rpm range that was causing massive back fires and it seems good. I am going to swap my Cap and Rotor again for some AC delco parts as the Neihoff cheaper lordco parts don't seem happy even with new NGK big leads on it I got a shock off the dist. so I think that it might have a very fine crack or possibly just thin casting on the plastic but that will have to wait untill next week for pay day.


We went to the wrecker today for a new drac module for the dash I got off sanj and while we were out there I took my Sawsall and cut the rear floor pockets out for Bikehaulers van so he can mount a bench seat for his impending little. What a miserable job to get those out we snapped 4 blades and cooked the teeth off of 2 more. It took an hour and forty five to get the pockets out of course it would have helped if we didn't chop the frame in half with the saw.

[Clamster]

I'm with ya Kidhauler with your grief. Been there and am still there with my 'stro. All you have done is very good for the truck and costly, I've been raped by the prices on these cheese electrical parts.
Take a serious look at your egr valve, 2 bolts and a couple of choice words for GM engineering and you'll have it off. See if the valve moves easily manually, if not clean the caked up carbon out of it. This will be a cause of low speed backfires etc. Look at it this way-you've done everything else. A new gasket about one dollar for it. While ya got it off start the motor for a couple of seconds-have a rag over the general area of the valve cause it will blow alot of soot out. Re assemble-take a cruise and see if theres any improvement. Then have a couple cold beers and let us know. Autozone is the best site for pictorial how to's on stuff. Luck to ya. Bet its not a cam lobe as it would be constant not intermitant. These vehicles run great when they run great and are a mindgame thanks to all the electronic nonsense put on for emmissions. When I grew up a Cat was something ya fed an 02 sensor was something they took to the moon. How did we ever get by without throttel posisioning sensors,Maf etc etc.