I scanned codes on my 97 SLS and got P1108 that is current. I have put hours of work into this car and its knocking. Will a faulty Map Sensor cause engine knock?

 

No a bad MAP sensor won't make it knock but it will give you poor gas mileage. Possibly a cam sensor or crank sensor.

 

Fleetcoupe thanks for your reply.

I changed the crank sensors already. Will change cam sensor today. Cleaned EGR Valve and MAP Sensor. On a 97 SLS should I have crank sensors relearned?

Engine never knocked before I replaced head gaskets and timed again. I am more than 100 % sure it is timed correctly. All valves and pistons are clean. During cleaning I didn't lube walls for pistons. Could this cause piston rings to rip out of position causing knock?

I don't want to take engine apart again because I fear threads will rip out of block.

Any suggestions is more than appreciated.

 

Not putting the oil on the cylinder walls is preferable during teardown but the oil will get splashed onto the walls if you've had it running. Are you sure all sensor wires got plugged back in and not damaged?? Did you have a chance to pull any codes since startup?? Do you have any sort of predetonation sensor on that car??

 

Thank you for support Fleetcoupe.

I am sure all sensor wires are clean and plugged in correctly. Yes, I pulled codes and the only one that was serious was the MAP sensor(others were bad circuits to window switch). Yes, I do have a knock sensor that is suppose to prevent detonation/knock under the intake manifold in the middle of block. I understand that sensor is a very sensitive listening device. However, my car was overheating and I read somewhere that the excess heat will cause it to stop functioning properly.

I forgot to purchase a vacuum hose that I broke off. Someone drove car, put in regular gas, and I need premium. Just replaced spark plugs and they were black but dry, so I cleaned them with automotive paint thinner. Car is hard to start even after cleaning and re lubing starter internally.

Could the knock sensor be malfunctioning because car overheated a lot?
Missing vacuum line is not for fuel regulator. Could the missing line dramatically change fuel:air ratio and cause engine knock?
Is that black on spark plugs do to bad and or burnt fuel that is causing knock?
I hear fuel pump humming louder than me every time I turn key. Could hard starting and knocking be to clogged fuel filter causing a knock?

Thanks for reading my post I appreciate all suggestions.

 

Possible damage to knock sensor from overheating, Vac. line shouldn't cause knock, but depending where it goes, black plugs would be rich fuel mixture,hard start could be from fuel filter if it is dirty. Did you do a fuel pressure test?? The filter would not cause the knock.Fuel pump might be on the way out if it is getting really noisy. Do the pressure test to rule that one out.How is the temp. sensor??

 

Thanks for your reply Cadsforfun.

After purchasing vac line from junk yard I will pick up the temp sensor and fuel filter. I never would have suspected temp sensor but I learned the importance of it, Cadsforfun thanks for the heads up. I will perform fuel test. I am more confident about buying a new knock sensor but that will be last resort because its more expensive then vac line, filter, and temp. sensor.

I think I can see the FINISH LINE!

 

Today I managed to install new fuel filter, coolant temperature sensor, and vacuum lines are in the right position. The engine is still knocking and I will need an alternator soon. My next moves will be to get a new map sensor, cam sensor, and knock sensor. I ran the in dash diagnostics and the only serious code was P0107(map sensor low voltage). Before I cleaned map sensor I got the P0108(map sensor voltage to high). The intake manifold is almost spotless internally including throttle body.

The car is hard to start but after its started it fires up with no problem. I tap on the gas and it accelerates easy. After I release gas pedal the RPM drops to a little over 500, while battery light is flashing and no charge messages appears and disappears. Battery voltage is at 11.8. The alternator is installed right and tight, no corrosion on wires.

I will more than likely start with the MAP sensor because of the codes. Could it be anything I'm missing that is causing the MAP sensor to be at fault?

I have no other codes that is relevant to this knocking engine. If the MAP sensor wont do the trick should I replace the Knock sensor first or the Cam?

I already replaced the two crank sensors because the Autozone guy ran test and the only one that came up was no crank sensor detected. Do I have to do a re-learn procedure for the crankshaft sensors?

Because the Alternator is going out could it somehow be giving the computer false information because of low voltage?

 

Maybe run a compression test to check that your rebuilt heads aren't the problem.

 

A MAP sensor code could be set from having a vacuum leak. A vacuum leak can also cause a knocking noise, or "Ping". I chased a MAP code on my '94 for a long time before finding a vacuum leak was causing the code to set. Any unmetered air that is getting into the engine can set a MAP code.