I have an 02 vert with some mods heads cam long tubes etc. The car has been fine for the last 5 months since all mods were done and tuned.

Well the other day i was on my way home from a 2 hr trip and about half way home the car started to lose power and miss badly. I managed to get the car home and ran a heap of checks.

Here is what i have done so far.

Check for codes. NO CODES

Check leads and plugs all ok even replaced them with my old set which i know were working fine when removed to make sure and still the same.

Checked each coil pack individulally by replacing one at a time with a brand new one i bought just to make sure not being caused under load or heat related.

Checked engine earth straps seem to be fine.

Removed each injector plug one at a time while running to see if fuel related.

Before you ask about fuel it had a full tank of high octane fuel in it before i left to go on the trip and i had used about half a tank before the problem occoured and had not topped up anywhere along the way.

Anyway after spending the whole day checking all these things the problem went away and the car was running fine. So i thought i might have possibly picked up a bit of crap in the fuel system and it passed. So i drove the car again yesterday one and a half hour trip to where i was going, all was good on the way there but on way home it happened again. I drove the car real steady for around 10 miles and it cleared again and started running fine.

The only thing i have not checked yet is fuel filter as i replaced it about 1500miles ago and have not had injectors out and bench tested.

car plays up the most around 2200 to 2500rpm. Once you go past that rev range seems to get better but can still feel the miss.

ANY HELP OR IDEAS WOULD BE GREATLY APPRECIATED.

 

Did you check the fuel pressure when this happens ?

 

Not yet need to get a guage.

is it common for a fuel pump to play up intermitantly. I thought electric pumps just stopped working.

What fuel pressure should they have?? Seems the car is worst at under 2500 rpm when it plays up.

 

Reading your post, you had no codes...You may want to get with the "tuner" to understand what was done as a mis-fire should produce some codes...

 

I would think this would generate codes, but check the ground wires on the rear of the driver's side head and make sure they are tight.

 

I spoke with the tuner a few times and he said fuel pressure issue will not produce codes and now with the tune earth issue will not always produce codes either and is much harder for the car to go into limp mode because of things in the tune.

 

I checked the earth on the engine block to chassis rail looked ok. I have also put on a heavy gauge earth cable from engine block to chassis when i did the heads cam about 5 months ago and it was also secure.

I will check the one on the back of the head.

 

I had this happen and had a bad plug. But, I guess you said you checked that.

 

I wish it was a bad plug as that would have been an easy fix. I have changed plugs and leads and checked all coil packs by replacing one at a time with no change.

 

Ok, so it's sounds like you have inspected G105(lower left side of block), and G107(behind driver head), what about G106 above the starter? Since you have headers, I would also inspect the wiring to the crankshaft sensor, and front O2's for heat damage/melting/shorting.

 

Checked all earths all good and were tight.
Pulled fuel filter off and drained it. Had some particled in the bowel when i draied it. Was not restricted or blocked. I am thinking i may have had some crap pass through it and possibly block an injector and it passed through it as it now seems fine. I drove the car around all day and it did not miss a beat.
It's got me f@#ed what's going on with it.

 

Additional info, could be tough to troublshoot as you have no codes...

From AutoTap

http://www.autotap.com/Engine-stalls...r-misfire.html

PROBLEM #7: CHECK ENGINE LIGHT ON, P0300 RANDOM MISFIRE CODE
A random misfire means your engine is misfiring, but that the problem is not isolated to one or two cylinders. It is jumping around in a random way from one cylinder to another. A random misfire code usually means the air/fuel mixture is running lean. But the cause might be anything from a hard-to-find vacuum leak to dirty fuel injectors, low fuel pressure, a weak ignition coil, bad plug wires, or compression problems. Even a dirty MAF sensor can cause a lean code and/or misfire to occur. The engine may be stalling because it isn’t getting enough throttle opening. The cause is often a problem in the idle air control system. The first thing to check is the intake vacuum with a vacuum gauge. On most vehicles a normal reading is 17 to 21 inches Hg. If the needle is lower, is jumping up and down or steadily dropping, you have a vacuum problem. Look for possible vacuum leaks by checking vacuum hose connections, the throttle body and manifold, and PVC valve and plumbing. An EGR valve that is leaking can also act like a vacuum leak and cause a random misfire. The next thing you should check is the fuel pressure with a gauge. If it is not within specifications (refer to a service manual for specifics because fuel pressure is critical for proper engine performance), the problem may be a weak fuel pump, low voltage to the pump (check the relay and wiring), or obstructions in the fuel line (like a plugged filter). A bad fuel pressure relay can also leak pressure and prevent an otherwise good fuel pump from delivering full pressure to the injectors. Dirty injectors can also restrict fuel delivery and cause a lean fuel condition. Many regular grades of gasoline do not contain adequate levels of detergent to keep the injectors clean. Frequent short trip driving accelerates the buildup of injector deposits. Cleaning the injectors with a good quality fuel tank additive (or having them professionally cleaned) can solve this problem. Look at short term fuel trim (STFT) and long term fuel trim (LTFT) with your scantool or scanner software. If the numbers are high, it tells you the engine is running lean.

PROBLEM #8: CHECK ENGINE LIGHT ON, P030x SPECIFIC-CYLINDER MISFIRE CODE One of the impressive features of OBD II systems is the ability to self-diagnose a misfire and pinpoint which cylinder has the problem.+ For example, P0302 indicates a misfire on cylinder #2. A cylinder specific misfire indicates that either compression, appropriate fuel mixture, or spark is missing. Start with a visual inspection, looking for a vacuum leak near the cylinder and any sign of wear on the spark plug wire. Check the compression on the target cylinder to ensure that the engine is mechanically sound. Use a stethoscope to listen to the suspect cylinder’s fuel injector. Listen for distinctive clicks and compare to another cylinder

 

Well have checked for vacume leaks with gauge. Vacume is stable with no leaks. Drove car around today car did not miss but i did notice some knock (pinging ) when i loaded it up at low revs. Car never did this before not even on the dyno when it was tuned.

I am now quite sure i must have got a bad tank of gas due to there being particles in the fuel filter when i drained it.

I still have half a tank in the car and i need to drain it out. Anyone know if the C5's have a drain plug in the gas tanks.

I want to get this gas out and change the fuel filter and see what happens.

 

I had the same problem and it was my MAF sensor, it had to be replaced. Also make sure the wires running to the MAF are good without any exposed area that could be arcing.

 

Definately not the MAF as i dont have one. I am running maffless tune.

 

Also know as a SD tune (Speed Density)

No drain plug(s) on the tanks. I don't have the procedure, but there is one for using the factory pump to pump the tank empty by jumpering the fuel pump relay with the (driver's side) fuel tank outlet disconnected and a piece of vinyl tuning clamped over the outlet nipple.

I agree it could possibly be a fuel delivery/bad fuel issue. In addition to the obvious filter (which has a built-in pressure regulator too, btw) that you mention, checking the fuel pressure will be a help too. Nominal pressure should be 58 psi (~). Also check closely the injector wiring harnesses, especially on the pass. side where it goes around back behind the intake manifold area. Make sure it's not chaffed/cut on one of the intake manifold hardware pieces, etc.

HTH