need serious help with my 97 bravada PO300 error

[tfrance02]

i have a 1997 bravada which i have had for 5 years and really havent had anything go wrong with it, only had to replaced a head gasket in this time. Then it went down hill fast. while i was driving my truck shut off for a split second and come right back on. did this a couple times i put in some fuel cleaner and 2 weeks went by with no problems. Then while driving my truck just shut off and would not start back up. So i have it towed to my mechanic(working on my cars since i was 16) he does a tune up, i.e. plugs,wires,fuel filter. and it runs. i notice it runs a little louder then it used to but it worked, then 2 weeks go byand my truck has no acceleration. so i take it back to the mechanic and i get my water pump replaced(needed to be done was leaking for a while) he says first off should be the pcv valve, i say okay cool . he calls back 2 days later and its not the pcv, and he thought it was the fuel regulator, but still that wasn't it. so i pick up my truck still running really really rough and he tells me its the computer. i say okay. i then take it to another shop that my work gos thru and they tell me its brining up a couple error. maf sensor error and a PO300 misfire error. so i repalce the mass airflow sensor,clean my k and n air filter and replace the ignition coil. truck seems to work a little better but not much. so this is where i am now. i have been reading on the interent how it could be 7 or 8 different things. what i think it might be is either the fuel injectors, the cat, or the map sensor. I really need some help with anybody that has problems like this before. also was told it could be the fule pump because the psi is a little low.

long read but hopefully somebody on here can help me out

Thanks for reading

Thomas

[Chris Stewart]

Ahhh, the dreaded P0300-Intermittent Cylinder Misfire/all cylinders-no particular cylinder.
The fuel pressure needs to be 63-66psi.
Get rid of the K&N and get a plain paper filter...the filter oil gets on the MAF sensor and messes with the signal.

I don't know how to clean a MAF sensor if it does get oily, all help gratefully accepted.

I have a picture somewhere of dirt & oily residue on my turbo blades from using this filter on my Cummins. Dirt & residue hasn't been back since changing to paper.
You might change where you're buying fuel since it's been so rainy this year. Try to locate non-alky fuel. Exxon doesn't use alcohol here.

[tfrance02]

Thanks for the response, ya i know this is such a wide open problem. i am getting a new map sensor. plus i am looking for a stock air intake. my only question about the k an n air intake i have is. i have had it on for 5 years with no problems you think know it can be causing a problem? let me know

Thanks Thomas

[maxwedge]

CRC makes a maf cleaner that will clean up just about any MAF.

[old_master]

P0300 is almost ALWAYS due to a secondary ignition problem: Spark plugs, spark plug wires, distributor cap, distributor rotor, & ignition coil. The 4.3L is VERY fussy when it comes to ignition parts, they like AC Delco . You'll pay a little more for them, but it will run properly.

[tfrance02]

Thanks for all of the responses, the truck has new ac delco wires and plugs and ignition coil. shop repalced the distributor cap(don't know what kind). i believe the dist. rotor is the only thing i haven't repalced. this weekend i am going to repalce the map sensor and remove all of the wires and plugs and make sure none of them are faulty. any other tips would be great. thanks guys

[Chris Stewart]

Thanks for the CRC tip Maxwedge.

While you're looking in the distributor TFrance02, check the starwheel for cracks or slippage. I had a friend w/305 Monte Carlo that exibited your symptoms and the starwheel (reluctor) was cracked & slipping on the distributor shaft.

[frets14]

Hello, My name is Steve. I'm new to the Bravada forum, but have been on AF for a number of years on other forums. I am just now considering a trade on a 99 Bravada and have been looking over the forum for possible problems I might want to look out for if I get the vehicle. So much for the introduction.... About your P0300 error, I had a 95 Olds Silhouette with the 3800 engine in it that had very similar symptoms. The engine would intermittantly run really rough with cylinders not firing. The code on that van indicated that I had a bad MAF sensor and I replaced it first with a used one and then with a new one. It didn't help. I went through a lot of different electrical peripherials and still never solved the problem. Then one evening as I was revving the engine, thinking and trying to solve my problem I ended up spinning a bearing and we decided to just replace the engine. That was finally done and I figured my problem would be solved, but it wasn't. When I got the replacement engine from the salvage yard I also got the computer that went with it so I had that put in the van. Still had the same problem. After all this reading you've probably concluded that I went through a lot of time and money to get this problem resolved. You'd be correct... I had well over $1500 in the repairs and still had the problem. I had been dealing with a very knowlegeable and reputable company that does Automotive Electrical repair and after spending some time on it with me they found there was a bad connection in the wiring harness. The mechanic started tracing the wiring back from the MAF sensor and when he twisted on the wiring harness he was able to recreate the problem while the car was idling. Within an hour they had tracked down and repaired the faulty connection and I never had the problem again. I don't know if this is your problem, but everyone involved in the repair of my van was so busy thinking about the different electrical components that might cause the problem that the wiring between those components was completely forgotten. I hope this helps.

[Chris Stewart]

Thanks frets14, sometimes we need to be reminded wiring is subject to the same problems as components.

[tfrance02]

thanks everybody for all of the posts, well truck still is running bad, picking up a computer this weekend for cheap that i can have programmed(friend works at a dealer). the one thing that bothers me about this whole thing is my truck will just shut off sometimes. the other day it just shut off. gauges froze the whole 9 yards. i think it has to be a short some place or a bad computer know. i'll let you guys know what i find out when i replace the computer