Runs really bad at idle!

[ajaxajax2000]

I now had my ZR-1 '92 for 4 weeks. Since two days it has started act really weard. When I start the engine not touching the throttle it runs extreamly unevenly in a kind of slow and pulsating way. Like it's running on just half of it's cylinders. Reminds me of my old Harley (which shall run just like that at idle). Once I rev it up to 4K a couple of times it starts running normally at idle. If I don't rev the engine, but just put it in 1:st and start driving, the car feels very week and jumpy for like 10 - 20 mtrs. Then with a distinctive jolt it enters "normal" mode. When driving, the engine seems normally strong and fast.

This behaviour is the same wheter the engine is cold or hot. If I drive for one hour, stop and start, it's just the same.

Just about the time this problem started I got the "service engine soon" light on the warning display.

Any ideas, someone.

TIA

Peter

[Aurora40]

Well definitely find out what code is setting the SES light first. :)

[ajaxajax2000]

Ok, and how exactly is that done? I read about connecting different contacts with a paperclip, but could someone please explain in more detail how I go about this? :worship:

Peter

[tccrab]

Turn ignition switch to "Off".
Ground ALDL terminal "B" to ground ("A").
Consult the manual pg. 6E-6 for picture of ALDL connector.
Turn ignition switch "On".
The "Service Engine Soon" light should flash Code 12 three (3) times,
followed by any other codes (in numerical order from lowest to highest), which may be stored.
Each code will flash three (3) times.
After all the codes are displayed, the sequence starts over with "12" again.


ZR1 ECM CODES 1990 TO 1992:

Code #12: Normal No Codes.
Code #13: Left Oxygen Sensor Circuit.
Code #14: Coolant Temperature Sensor Circuit High.
Code #15: Coolant Temperature Sensor Circuit Low.
Code #16: Direct Ignition System (DIS) Fault Line Circuit
Code #21: Throttle Position Sensor Circuit High.
Code #22: Throttle Position Sensor Circuit Low.
Code #23: Manifold Air Temperature Sensor Circuit Low.
Code #24: Vehicle Speed Sensor Circuit.
Code #25: Manifold Air Temperature Sensor Circuit High.
Code #31: Camshaft Sensor Circuit.
Code #33: Manifold Absolute Pressure Sensor Circuit High - Low Vacuum.
Code #34: Manifold Absolute Pressure Sensor Circuit Low - High Vacuum.
Code #36: Direct Ignition System (DIS) Circuit (missing or extra EST signal)
Code #41: Cylinder Select Error (Faulty or Incorrect Mem-Cal)
Code #42: Electronic Spark Timing (EST) Circuit.
Code# 43: Electronic Spark Control (ESC) Circuit.
Code #44: Left Oxygen Sensor Circuit Lean.
Code #45: Left Oxygen Sensor Circuit Rich.
Code #46: Vehicle Anti-Theft System (VATS)(PASS-Key) Circuit.
Code #51: Mem-Cal Error.
Code #52: Engine Oil Temperature Sensor Circuit Low.
Code #53: System Voltage.
Code #54: Fuel Pump Circuit (Low Voltage)
Code #55: System Voltage
Code #56: Vacuum Sensor Circuit.
Code #61: Secondary Port Throttle Valve System.
Code #62: Engine Oil Temperature Sensor Circuit High.
Code #63: Right Oxygen Sensor Circuit Open.
Code #64: Right Oxygen Sensor Circuit Lean.
Code #65: Right Oxygen Sensor Circuit Rich.

The above codes are specific for the ZR1's (Vin J). Page 6E3-A-1 1990 Helms Service Manual

TomC
'90ZR1 #792

[ajaxajax2000]

Got it. And thank's for all the codes. Just one question - how do you know it's terminal K that shall be grounded? :icon_scra

Peter

[tccrab]

Got it. And thank's for all the codes. Just one question - how do you know it's terminal K that shall be grounded? :icon_scra

Peter

Peter:

Oops, terminal K is for the SIR (airbags).
I copied and pasted from the trouble shooting section, I failed to notice that it was diagnostics for the SIR and not the ECM. :rolleyes:
The two you want are terminals A & B, A is ground, B is the ECM diagnostic.

The ALDL (Assembly Line Diagnostic Link) is located under the instrument panel and is covered by a plastic cover labeled "DIAGNOSTIC CONNECTOR".
It is used in the assembly plant to receive information in checking that the engine and other computer systems are operating properly before it leaves the asembly plant.
The ALDL pins are configured like so:
____________________
| F | _ | _ | C | B | A |
| G | H | J | K | L | M |
-----------------------

A = GROUND
B = ECM DIAGNOSTIC
C = RIDE CONTROL DIAGNOSTIC
F = T.C.C (vin 8)
G = CCM DIAGNOSTIC
H = ANTILOCK BRAKES
J = E & C BUS DATA
K = SIR DIAGNOSTIC
L = SIR SERIAL DATA
M = SERIAL DATA (data line used by Tech1 Diagnostic Computer to read system data information for the ECM, Anti-Lock Brake and CCM.

TomC
'90ZR1 #792

p.s., have you checked your MAP sensor hose?

[GrayZ]

i was gonna suggest checking the map sensor hose...if it is soft, that might be your problem..mine acted the same way last year and was corrected after installing a new hose...

[Jeffvette]

Should be black smoke coming out of the exhaust, especially if it's giving you a SES light.

Reach behind the plenum and see if the hose popped off the plenum fitting, or if the hose completely seperated.

Always make sure you hold the key over when starting, and do not release until it has completely caught. This will eliminate the backfire 99.9%

[ajaxajax2000]

Jeez. You guys really are supportive! I've consulted the manual about the MAP sensor, and it doesn't mention any hose, but I'll have a look under the hood and see if I can find it on your description. Be back on this I guess. :mad:

Thank's a lot!

Peter

[ajaxajax2000]

Sure enough. It was the MAP sensor hose. ECM code 33 and a loose sensor hose. Which is now in place again (a litle soft, needs to be replaced, I guess) and the car runs like a charm on idle. :D

A big thank's to all who helped out! :thumbsup:

Peter

[tccrab]

Sure enough. It was the MAP sensor hose. ECM code 33 and a loose sensor hose. Which is now in place again (a litle soft, needs to be replaced, I guess) and the car runs like a charm on idle. :D

A big thank's to all who helped out! :thumbsup:

Peter

Great news! :thumbsup:

Glad to be of help.

Get in it and DRIVE it! :hello:

TomC
'90ZR1 #792

[Z Factor]

Sure enough. It was the MAP sensor hose. ECM code 33 and a loose sensor hose. Which is now in place again (a litle soft, needs to be replaced, I guess) and the car runs like a charm on idle. :D

A big thank's to all who helped out! :thumbsup:

Peter


Isn't it great when you find a simple inexpensive fix to a frustrating problem?

Jeff's advice about not releasing the key to quickly when starting is absolutely correct and should prevent it from happening in the future.

:cheers:

[ajaxajax2000]

Isn't it great when you find a simple inexpensive fix to a frustrating problem?

Jeff's advice about not releasing the key to quickly when starting is absolutely correct and should prevent it from happening in the future.

:cheers:

Certainly is. And I learned a thing or two at the same time.

Thank's again! :cheers:

Peter