Help!! 91 missing/underpower issue - ZR-1 Net Registry Forums

SDZR-1 · 09-01-2007

Ok...been experiencing this for about 3 days now...pulled codes and only found throttle position sensor to be too high but it was only showing .3 volts. service engine light came on twice today for about 5 seconds each time. to describe it best there is a clattering sound (sounds similar to a lifter clattering) that comes from underside of engine (maybe tranny, I cant tell for sure) that goes away with a bit of throttle. it is also missing and has less than superior power, although I can feel the secondaries open up at full power. I have spark to all plugs. I dont know what else to check, any tips would be greatly appreciated. Also, fuel mileage seems to have dropped quite significantly.

thank you
Jarvis Bruhn

gbrtng · 09-02-2007

Quote:

Originally Posted by SDZR-1

Ok...been experiencing this for about 3 days now...pulled codes and only found throttle position sensor to be too high but it was only showing .3 volts. service engine light came on twice today for about 5 seconds each time. to describe it best there is a clattering sound (sounds similar to a lifter clattering) that comes from underside of engine (maybe tranny, I cant tell for sure) that goes away with a bit of throttle. it is also missing and has less than superior power, although I can feel the secondaries open up at full power. I have spark to all plugs. I dont know what else to check, any tips would be greatly appreciated. Also, fuel mileage seems to have dropped quite significantly.

thank you
Jarvis Bruhn

Pull the spark plugs - bet you find a bad one ...
What is/are the SES code(s) ?

tomtom72 · 09-02-2007

The clattering may be a loose heat shield....I have one & at the right rpms I hear it & then it quiets down once I pass the resonance spot.

Miss....all the time or no? Checked the whole ignition system; plugs, wires, coils all are good. Did you pull any plugs to see how they are burning? Did you scan it to look at the fuel numbers? Did you scan to check the CCM for any history codes?

Gas milage going south + a miss; I say you will find something on a scan, JMHO. Are the injectors the OEM set? Remember 90 & 91 are not ethanol proof. When you get to the secondaries the miss goes away? Does she smell lean or rich out the exhaust at idle? Forgot this, how's the fuel system; pumps, regulator & filter?

FSM, section 6E, drivability & emissions is a place to start looking up your symptoms. There is also a page there with scan data for a normal LT5 in closed loop.

Tom

SDZR-1 · 09-02-2007

yes...it misses all the time; at idle and while driving. I will pull the plugs today and check that. From what I had been reading, it sounds like it could be the primary injectors....which I think I will change regardless when I put in my new starter since I believe they are oem....either way, I would still like to determine the problem before hand. thanks for the replies guys, and keep any other suggestions coming...I definately appreciate the feedback.

tomtom72 · 09-02-2007

Okay now we're getting somewhere! If it misses all the time my next Q will be;

does the miss get worse as the motor comes up to proper operating temp?
If yes then it's not looking good for the OEM injectors.

Q2; Do you know what a lean condition smells like? Stand behind the car & get a good wiff of the exhaust...if it makes your eyes water &/or smells kind of acrid then ya have a lean burn....bad injectors, maybe.

Q3; did you run down any DTC's? Post up if you have them.

Q4; do you have a scan tool, need that to look at the fuel numbers. Oh, and a FSM.

Q4; Did you pull any plugs & take a look at the burn pattern? Do they look too clean, do they look dry, like they saw no gas? If so the fuel filter is blocked solid or the primary injectors have coil failure. Outside shot could be the injector drivers in the ECM, or maybe bad injectors relays. You have good fuel pressure?

FWIW, you can test the ohms reading on the injectors thru the ECM harness but ya need the FSM for the pin numbers. I believe above 16-18 ohms is okay but don't quote me on that one. Oh, if you ohm them you should do them stone cold and after the motor gets hot. Usually they break down more severly the hotter they get.

My guess....just a guess mind ya...is the primaries sound like the have died & gone to meet their maker.

Tom

SDZR-1 · 09-03-2007

no...dont have a scan tool. but had a guy i know plug his in and all it came up w/ was that code 21 throttle position sensor too high. I found a fouled plug after pulling them out, so tomorrow I will just replace all of them and go from there...i'll let you know, thanks again

09-01-2007	#1
SDZR-1 Join Date: Aug 2007 Location: Bison, SD Posts: 106	Help!! 91 missing/underpower issue Ok...been experiencing this for about 3 days now...pulled codes and only found throttle position sensor to be too high but it was only showing .3 volts. service engine light came on twice today for about 5 seconds each time. to describe it best there is a clattering sound (sounds similar to a lifter clattering) that comes from underside of engine (maybe tranny, I cant tell for sure) that goes away with a bit of throttle. it is also missing and has less than superior power, although I can feel the secondaries open up at full power. I have spark to all plugs. I dont know what else to check, any tips would be greatly appreciated. Also, fuel mileage seems to have dropped quite significantly. thank you Jarvis Bruhn

09-02-2007	#3
tomtom72 Join Date: Dec 2004 Location: Jacksonville, FL USA Posts: 4,609	Re: Help!! 91 missing/underpower issue The clattering may be a loose heat shield....I have one & at the right rpms I hear it & then it quiets down once I pass the resonance spot. Miss....all the time or no? Checked the whole ignition system; plugs, wires, coils all are good. Did you pull any plugs to see how they are burning? Did you scan it to look at the fuel numbers? Did you scan to check the CCM for any history codes? Gas milage going south + a miss; I say you will find something on a scan, JMHO. Are the injectors the OEM set? Remember 90 & 91 are not ethanol proof. When you get to the secondaries the miss goes away? Does she smell lean or rich out the exhaust at idle? Forgot this, how's the fuel system; pumps, regulator & filter? FSM, section 6E, drivability & emissions is a place to start looking up your symptoms. There is also a page there with scan data for a normal LT5 in closed loop. Tom __________________ 1990 ZR-1, Black/grey, #2233, stock. ZR-1 Net Reg Founding Member #316 & NCM member Last edited by tomtom72; 09-02-2007 at 08:26 AM.

09-02-2007	#4
SDZR-1 Join Date: Aug 2007 Location: Bison, SD Posts: 106	Re: Help!! 91 missing/underpower issue yes...it misses all the time; at idle and while driving. I will pull the plugs today and check that. From what I had been reading, it sounds like it could be the primary injectors....which I think I will change regardless when I put in my new starter since I believe they are oem....either way, I would still like to determine the problem before hand. thanks for the replies guys, and keep any other suggestions coming...I definately appreciate the feedback.

09-02-2007	#5
tomtom72 Join Date: Dec 2004 Location: Jacksonville, FL USA Posts: 4,609	Re: Help!! 91 missing/underpower issue Okay now we're getting somewhere! If it misses all the time my next Q will be; does the miss get worse as the motor comes up to proper operating temp? If yes then it's not looking good for the OEM injectors. Q2; Do you know what a lean condition smells like? Stand behind the car & get a good wiff of the exhaust...if it makes your eyes water &/or smells kind of acrid then ya have a lean burn....bad injectors, maybe. Q3; did you run down any DTC's? Post up if you have them. Q4; do you have a scan tool, need that to look at the fuel numbers. Oh, and a FSM. Q4; Did you pull any plugs & take a look at the burn pattern? Do they look too clean, do they look dry, like they saw no gas? If so the fuel filter is blocked solid or the primary injectors have coil failure. Outside shot could be the injector drivers in the ECM, or maybe bad injectors relays. You have good fuel pressure? FWIW, you can test the ohms reading on the injectors thru the ECM harness but ya need the FSM for the pin numbers. I believe above 16-18 ohms is okay but don't quote me on that one. Oh, if you ohm them you should do them stone cold and after the motor gets hot. Usually they break down more severly the hotter they get. My guess....just a guess mind ya...is the primaries sound like the have died & gone to meet their maker. Tom __________________ 1990 ZR-1, Black/grey, #2233, stock. ZR-1 Net Reg Founding Member #316 & NCM member

09-03-2007	#6
SDZR-1 Join Date: Aug 2007 Location: Bison, SD Posts: 106	Re: Help!! 91 missing/underpower issue no...dont have a scan tool. but had a guy i know plug his in and all it came up w/ was that code 21 throttle position sensor too high. I found a fouled plug after pulling them out, so tomorrow I will just replace all of them and go from there...i'll let you know, thanks again