Idle, CEL, and smoke problems

[MarkB]

My current setup includes:

1. CTSC (6 lb. kit)
2. CT SMU (soldered in place)
3. Walbro fuel pump (from SOS)

The symptoms of the problem are:

1. CEL with codes 1201-1206, 0300, and 1399
2. Bouncy or no idle
3. Cold-start smoke w/ gasoline smell

Discussion:

The CEL issues occur at cold start. Not every cold start invokes a CEL and the CEL sometimes occures when the engine is warm. Once the codes are cleared the engine seems to run fine.

Frequently, the engine dies when I let off the gas and other times the resulting idle bounces from what appears to be zero RPM to about 1,100-1,200 RPM. At idle the exhaust has a gas smell.

The cold-start smoke/smell issue is very noticable. The aroma is that of a small amount of gas not oil.

The frequency of these issues has increased in recent weeks.

I spoke to my mechanic about these issues and we came up with a few possibilities.

• Dirty throttle body
• Injectors not closing properly (codes point to all cylinders and start-up smoke smells of gas)
• Coil-packs/igniters not delivering enough spark
• Bad CT SMU (staying rich at idle)

Might anyone here have some additional insight into this/these problems?

What order should I proceed in further debugging these issues or replacing parts?

TIA

 

[Larry Bastanza]

Hi Mark,

I would do the following:

1. Compression Test - This will eliminate any possibility of any internal engine mechnical issues.

2. Fuel Pressure Test - This would point towards the last item in the list above. - Bad CT SMU (staying rich at idle)

Thes are both fairly inexpensive diagnostic procedures. LEt's see what they turn up.

HTH,
LarryB

 

[NetViper]

Just incase you have not looked it up or if anyone is wondering what those codes mean.

P1201 Cylinder 1 Misfire
P1202 Cylinder 2 Misfire
P1203 Cylinder 3 Misfire
P1204 Cylinder 4 Misfire
P1205 Cylinder 5 Misfire
P1206 Cylinder 6 Misfire

P0300 Random Misfire

I could not find P1339. Larry, do you know what that is?

 

[drew]

Check the oil level of your CTSC.

I'm digging through a problem where an overfilled CTSC dripped down into the #1 and #2 cylinders. Those plugs were completely fouled...engine idled awful.

Drew

 

[Yellow Rose]

Two Other Items

Perhaps the ignitor (located on top of the throttle body) is not sending enough spark to the coil packs.

My memory is vague, but isn't there a resistor box on the passenger side of the engine bay that controls current to all six of the injectors?

 

[WOODY]

My memory is vague, but isn't there a resistor box on the passenger side of the engine bay that controls current to all six of the injectors?

I think this was only on OBD I

 

[DDozier]

Hi Mark,

I would do the following:

1. Compression Test - This will eliminate any possibility of any internal engine mechnical issues.

2. Fuel Pressure Test - This would point towards the last item in the list above. - Bad CT SMU (staying rich at idle)

Thes are both fairly inexpensive diagnostic procedures. LEt's see what they turn up.

HTH,
LarryB

Mark follow the Larry,

The Comptech FPR may have a week spring and causing a rich condition at idle. Fuel pressure test at idle, with key on not running, and a few other readings like 3000 RPM and 5000 RPM will tell us that.

Does the newer Comptech kits still use the pressure switch in the bottom of the intake to activate the boost-a-pump, if so this may be shorted, a voltage reading at the fuel pump while at idle and while on boost will tell us if the boost-a-pump is working correctly.

While you have a plug out take a picture and post a closeup of the electrode. Should look very rich, but if it is only on one plug then you may have a leaky injector.

Dave

 

[RacerX-21]

Just incase you have not looked it up or if anyone is wondering what those codes mean.

P1201 Cylinder 1 Misfire
P1202 Cylinder 2 Misfire
P1203 Cylinder 3 Misfire
P1204 Cylinder 4 Misfire
P1205 Cylinder 5 Misfire
P1206 Cylinder 6 Misfire

P0300 Random Misfire

I could not find P1339. Larry, do you know what that is?

The connector/harness on the rear side of the igniter has a ground wire that needs a very good ground connection, if you have paint, corrosion or even a not so tight application from stripped threads, the igniter will have problems. Maybe this is your problem, I have seen this before and if I remember correctly the Comptech kit uses a special short bolt that is prone to stripping.

 

[MarkB]

...1. Compression Test - This will eliminate any possibility of any internal engine mechnical issues. ...
...2. Fuel Pressure Test - This would point towards the last item in the list above. - Bad CT SMU (staying rich at idle)...

The compression test showed all cylinders at 180-190 lbs., a leakdown test showed between 10-20 % for all cylinders, the fuel pressure reading was 105 lbs (pre regulator), and a fuel pressure leakdown test showed a loss of 5 lbs in 10 minutes.

...I could not find P1339. ...

The final code is a 1399

...Check the oil level of your CTSC. ...

The oil level is not an issue. I do my own CTSC oil changes and make sure it is always properly filled.

...While you have a plug out take a picture and post a closeup of the electrode. ...

We checked all of the plugs and they were slightly carbon-covered, however, not excessively so.

The connector/harness on the rear side of the igniter has a ground wire ... special short bolt that is prone to stripping.

Do you have a way to post pics of the location of the bolt?

The result of a dyno pull performed w/ a wide-band sniffer is below. The O</SUB>2</SUB> is actually lean.

 

[drew]

The bolt in question is on the CT rear lower manifold on the throttle body side.

It is directly in front of the rear injector rail. Specificially in front of the LH rail fastener bolt.



Drew

 

[Larry Bastanza]

The compression test showed all cylinders at 180-190 lbs., a leakdown test showed between 10-20 % for all cylinders, the fuel pressure reading was 105 lbs (pre regulator), and a fuel pressure leakdown test showed a loss of 5 lbs in 10 minutes.

Sounds to me like your fuel pressure regulator is not working.

What is idle fuel pressure? If it is anywhere near the 105 lbs, your fuel pressure regulator is just not relieving pressure at all. Fuel pressure should be 46-53 lbs at idle, measured at the output of the fuel filter. Even with the SC at idle there is no boost so factory spec is still applicable.

This certianly coodinates with your symptoms.

See page 11-95 in the on-line service manual.

HTH,
LarryB

 

[MarkB]

The bolt in question is on the CT rear lower manifold on the throttle body side. It is directly in front of the rear injector rail. Specificially in front of the LH rail fastener bolt.

Found it. It was tight.

Yesterday, I cleaned the throttle body and low-and-behold all of my problems went away.