How can you tell if your knock sensor is bad?

Forever-Fiero · Post by **Forever-Fiero** » Wed Feb 04, 2009 8:23 pm

Hers the prob. I've got the TGP 3.1 in and running. Trying to work all the bugs out with much success. But this thing is knocking(backfiring) and I dont know why. Its getting fuel to the injectors at 45-50psi and I tested the injectors prier to install. I have 93 oct in the tank... the only other thing is timing. I think thats the prob. but idk. Been raking my brain for to ling and just need some fresh thought. Thanks

Oh. and one more thing. once I get it right and running smooth. I'll make a build thread if it will help others.

Tony.

darkhorizon · Post by **darkhorizon** » Wed Feb 04, 2009 10:32 pm

Knocking is pinging... and your car pretty much runs like normal and it just makings a real pinging noise at wide open... Thats basically your pistons getting really f'in pissed.

If it was bad it would throw a code, and run in a strange low timing mode possibly.. just giving you crappy performance, but mostly unchanged general operation.

The Dark Side of Will · Wed Feb 04, 2009 11:08 pm

knock =/= backfire

Got a scan tool?

Forever-Fiero · Post by **Forever-Fiero** » Thu Feb 05, 2009 11:44 am

darkhorizon wrote:Knocking is pinging... and your car pretty much runs like normal and it just makings a real pinging noise at wide open... Thats basically your pistons getting really f'in pissed.

Thats just it. The backfiring clears out an higher RPMs. Not 100% but like 98.9%.

The Dark Side of Will wrote:knock =/= backfire. Got a scan tool?

Yha but I need to wire up the dig port still yet. I'll do that today.

Forever-Fiero · Post by **Forever-Fiero** » Thu Feb 05, 2009 2:05 pm

Ok Did the code test(Using the tried an true ground A to B trick) and get the flash 1 flash 2. Thats to let me know its grounded. Next I get a flash 3 flash 3. And thats it. Dont know what that means because I cant fined my damn Haynes man. so can someone help with that?

From what I gather its looking like it may be a bad/leaking injector. Backfires at idle. Also hard to start when cold. fuel psi is up and no leaks in the line. But the fuel psi drops to like 10/15 when the fuel pump shuts off.

Found my book! 3/3 is MAP sensor. But I was f-ing with it earlier today. I pulled the vac line to check it. its working. I'll do the volt test on it to make sure.

p8ntman442 · Post by **p8ntman442** » Thu Feb 05, 2009 2:48 pm

If you were fucking with it, thats probably why you have the code. Clear the codes and try again.

Forever-Fiero · Post by **Forever-Fiero** » Thu Feb 05, 2009 5:23 pm

uh yha. I know thats why it through the code. thats not the problem. Thats what I was saying. Its not showing any other cods.

The Dark Side of Will · Thu Feb 05, 2009 6:30 pm

If the comp set the code, it'll take a minimum number of engine starts to clear the code, even if the sensor is plugged back in and working.

Forever-Fiero · Post by **Forever-Fiero** » Thu Feb 05, 2009 8:11 pm

Codes cleared. Theres no Falt. Still backfiring. Ggrrrr. ok im changing the injectors. The TGP injectors are 21.9 pph The only thing I have close that is LQ1 injectors witch are 29.7 pph.

Shaun41178(2) · Post by **Shaun41178(2)** » Thu Feb 05, 2009 11:16 pm

If the car backfires I am willing to bet that your plug wires are on the wrong cylinders.

Forever-Fiero · Post by **Forever-Fiero** » Fri Feb 06, 2009 9:04 pm

nop. not that either.

Blue Shift · Post by **Blue Shift** » Sat Feb 07, 2009 3:31 am

Crank position sensor wires? Carbon in the chambers?

The Dark Side of Will · Sat Feb 07, 2009 9:02 am

Forever-Fiero wrote:nop. not that either.

You sure?
Just the other day I chased a no-start around a VR6 VW for about an hour. The plug wires were on the right terminals, but the coil pack was bolted to the engine upside-down, which of course put them on the wrong cylinders.

Have you run a compression check?

Forever-Fiero · Post by **Forever-Fiero** » Sun Feb 08, 2009 12:57 am

Ok im going to replace the coils.I think one might be bad. Re check the wires. And no comp. test but I'll do that to. Will low comp. cause it to backfire? Whats the lowest It can be? 8.5-1 and all.

Aaron · Post by **Aaron** » Sun Feb 08, 2009 10:09 am

Why not test the coils first?

p8ntman442 · Post by **p8ntman442** » Sun Feb 08, 2009 1:04 pm

Because testing coils is bullshit. Ive had tested good coils let me chase the ignition module for weeks.

Aaron · Post by **Aaron** » Sun Feb 08, 2009 1:12 pm

I think it's pretty easy, and accurate.

With the engine running, and the coils not bolted to the ICM, remove a coil, and put it back on. If the engine's idle quality changes (And you'll know it), that coil is fine. If the engine's idle quality stays the same, that coil isn't.

Forever-Fiero · Post by **Forever-Fiero** » Sun Feb 08, 2009 6:37 pm

Shaun... Will... Yha um... Thanks for you tip. you guys are going to think Im a fucking TOOL/NOOB Dumb ass or other. 1 and 5. what do you know if you put them on the right plug and it fucking peers like a kitten. Damn. Ya know after building my wiring harness from scratch and the only problem I had that dealt with wires was a damn plug wire. I kinda feel good about that.

Thank you all for the help. Grrrr what a tool.

Shaun41178(2) · Post by **Shaun41178(2)** » Sun Feb 08, 2009 7:35 pm

Its always something simple right? Just glad you got it worked out. When I picked up my dohc turbo car it ran horribly and would sometimes backfire and just never reved correctly. I couldn't put my finger on it at first, but then I figured I would go over it just in case. Sure enough, 2 plug wires were backwards.

Time to start tuning that thing and having fun. Any pics of the swap complete?

Blue Shift · Post by **Blue Shift** » Fri Feb 13, 2009 9:52 pm

Forever-Fiero wrote:Shaun... Will... Yha um... Thanks for you tip. you guys are going to think Im a fucking TOOL/NOOB Dumb ass or other. 1 and 5. what do you know if you put them on the right plug and it fucking peers like a kitten. Damn. Ya know after building my wiring harness from scratch and the only problem I had that dealt with wires was a damn plug wire. I kinda feel good about that.

Thank you all for the help. Grrrr what a tool.

Happens. I had the same symptoms on first test start on my DOHC car. I crawled under and looked at the coils and the right wires were on the right numbers. I was slightly irritated, until I went to look at the book and the wiring was different - coilpacks were plugged in wrong spots, and wires plugged in according to number. Oops.

Yeah it's good to find out that the inch thick+ bundle of wire you traced out by hand one at a time works, and it was just a stupid plug wire, no?

Hey, speaking of, I have a 91 TGP drivetrain sitting in my garage that I hope to swap when I have some time. You using the original 440T4HD?

Real Fiero Tech

How can you tell if your knock sensor is bad?

How can you tell if your knock sensor is bad?

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