tee-boy

iTrader: (8)

any change in the valvetrain can cause backfire. slack in timing chain could cause it as well, but less likely.

Mike96z

iTrader: (78)

timing chain was first thought. but it was an engine from another party so you never know what they did beforre they sold it, couldve pulled a cam out and slapped the chain on wrong. but then again it would do it on both sides of the engine correct.

Mike96z

iTrader: (78)

Update. I replaced the coils but that didnt solve anything so sold the ones I bought for it. I put new plugs and new wires. I also checked the timing chain and all lines up. Still backfiring some and when I drive it, it seems like it doesnt wanna climb RPM's, like it struggles to do so. Well finally drove it about 1 or 2 blocks to the nearest autozone to get the codes read and here is what I found.

P0342 Camshaft Position Sensor Low Voltage
P0452 Fuel Tank Pressure Sensor Low Voltage

2 other codes were present but are EGR and egr is being deleted. P0443/P0449

As far as the first two codes go, Im going to replace the Camshaft position sensor, thinking its the main problem. Not sure what the fuel tank pressure sensor has to do with anything and I think it should run fine without it correct?

I'm still going to check fuel pressure and compression in each cylinder and hopefully the cam sensor fixes it. If I have good fuel pressure and still have a bad fuel tank pressure sensor, should I replace it?

If all fails, heads are coming off and Im checking for bad valves.



Let me know what you guys think.

Omec

iTrader: (2)

how many times did it log the cam sensor? do you just have a code reader or an actual scanner? that will def screw w/ ya. hopefully thats it. the fuel tank pessure sensor is for the evap system. you may have a vac line disconnected.

Mike96z

iTrader: (78)

Every code I listed was there twice, for some reason, all were doubled up in the system so it showed 8 codes, but probably because all codes were pending. I leave the car sitting with the battery disconnected. As far as the fuel system, im using the 97 Vette fuel rail with the regulator and return line system with a LT1 fuel tank/etc and walbro 255lph fuel pump so I got plenty of fuel but still havent check on pressure but did check for leaky injectors and had none.

ShevrolayZ28

iTrader: (4)

The SES light comes on once the error has occurred twice, so the scanner is just showing both times.

When you pulled the plugs did they all look the same? There may have been some diagnostic info there. It really does sound like it's not firing all cylinders.

Or perhaps you could measure heat off the headers with an infra red temp gage.

Another thought would be to check all the grounds, especially on the back of the DS head. Either reach way back there and feel for them with your hand or they can usually be seen from underneath the car.

GL

Mike96z

iTrader: (78)

Yea before I didnt know where those grounds went but they are all grounded behind the head now. Im going to check the cylinders soon but dont have the gun to do it. The car has ran the same when I first put the engine in with new plugs so it isnt the plugs but if I take a look at them, they basically looked normal. All coils, wires, plugs have been replaced, Im hoping this cam sensor does the trick. Can stand not having my V8 Z. Thanks

Mike96z

iTrader: (78)

Will update everyone after I replace the cam sensor and will get a new vid.

5.3LJimmy

iTrader: (10)

I thought it sounded like the cam sensor(post 19). I hope that fixes your problem.

Mike96z

iTrader: (78)

Thanks man.

Mike96z

iTrader: (78)

Umm. yea I found out that the cam sensor wasnt even plugged in. I hooked it up. The plug is what I believe went there. It was coming from the passenger side and was a very long wire that was separated with wire protector and had a 3 prong connector and I hooked it up but still popped and idles irregular. Im going to drive it around awhile and see if something changes. It does start up faster and should climb rpms quicker.

Rosco

I recently have been getting a backfire once every so often, after reading this thread I went out last night with multimeter in hand to check all my leads and plugs!

Found on the passenger side bank, one spark plug not completly tightly in, could be undone by hand and on the opposite side one spark lead was dead, couldnt get a signal through it at all, the core wire looked black too, all the other cables checked out fine!

These are the red MSD wires, what could cause something like this? could it be a coil?
im going to search as well, but incase I dont reveal any results

Mike96z

iTrader: (78)

Im not sure what would cause this. I have the red MSD wires and dont have a problem like that.

Rosco

Ive just ordered another set of the red MSD wires, shall put them on my car and keep 7 as spares!

Mike96z

iTrader: (78)

If the MAP sensor is unplugged, how much trouble would that cause. I know it measures intake pressure and adjusts timing or works with the MAF sensor for that.

Camaroz

iTrader: (2)

No need to sound fussy... People here are trying to help and Yes it is horrible to start a engine and just let it idle. It's not keeping it "fresh"

Mike96z

iTrader: (78)

Lol, have you seen an engine that has sat forever vs an engine that hasnt been started? it does keep it fresh. As I said its just personal preference I guess.

Soul TKR

iTrader: (4)

seafoam it

Mike96z

iTrader: (78)

whats the best place to do it?

Mike96z

iTrader: (78)

Had a fellow member come over with his HPTuners and try to reflash it with a stock tune. The car took the tune but it would not start nor run with a stock tune. So I had to keep the tune that was in the car. The tune had been modified from what we saw, the max rpm, max mph, and octane tables have all been touched. Nothing we tried worked except for the tune that was in the PCM which was not stock. So we ended up taking the tune that would start/run and removing the EGR/CAT codes and other codes that I did not need showing up, as well as turning misfires off.

So tuning the computer didnt work and it wouldnt take a stock tune which is wierd so the next move is to check fuel pressure, compression and then pulling the heads and checking for bent/burnt valves. The car is obviously missing at idle, the two guys I had looking at it noticed it immediately, also said there was alot of valvetrain noise.