Car not running right, RED HOT exhaust

[55Crestliner]

I know this isn't a car forum, but I know many of you are good with cars. Based on what the car is doing, I bet someone may have a clue - even if they've never touched a VW...<br /><br />I have been trying to fix a friends 91 Jetta. It was parked for several months. When he went to drive it last, he said it didn't have any power. It started for me, but it was very slow to rev. I shut it off and I could not get it to start for several days.<br />Here's a list of stuff I've done...<br /><br />Static timing - Everything looked/looks good.<br />Changed spark plugs - All were cruddy, one was loose.<br />Checked for intake blockage - no mouse nest in airbox.<br />Dropped cat, to see if melted down and blocking - would not start with cat off, cat's not the problem.<br />Did electrical tests on Harness going to computer according to Bentley manual - all good.<br />Swapped Digifant computer with one from my Golf (my Golf runs great) - still won't run right.<br />Swapped Fuel Pressure Reg with my Golf's, - no change.<br />Put a tester on fuel rail harness, it is pulsing, not constant on - that's good.<br />Compression test shows 145-150 on all four.<br /><br />I can SOME TIMES get the car to start, after numerous tries. The last time I tried, it was still very slow to rev, won't stay running unless hitting the gas, and I smelled something hot, saw smoke coming from the middle of the car. I looked underneath, and the pipe was completely glowing red, from the cat all the way to the muffler.<br /><br />When I take the spark plugs out, 1,2,3 are sooty, and wet. #4 is clean and wet.<br /><br />I have absolutely no idea what to do next.

 

[Dunaruna]

Re: Car not running right, RED HOT exhaust

We can get manifolds glowing red hot on the dyno, but thats at constant high RPM. If you're getting the exhaust glowing at idle you probably have a blockage downstream of the cat, the honeycomb can break loose and jam further down the line. That would also make it hard to start.<br /><br />Is there connection points that you can pull apart downstream of the cat?

 

[ob]

Re: Car not running right, RED HOT exhaust

Not positive ,but it could be a faulty o2 sensor causing fuel rich mix.

 

[BOBPELL]

Re: Car not running right, RED HOT exhaust

A partial blockage is possible - check that first.<br />From description timing belt may have jumped a tooth or 2. How many miles are on the T belt?

 

[FLATHEAD]

Re: Car not running right, RED HOT exhaust

My first guess would be a too advanced timing. Maybe an intake leak causing a lean condition. but then the plugs would be white??

 

[Bob_VT]

Re: Car not running right, RED HOT exhaust

Is it injected? A stuck injector or two will cause the exact situation... red exhaust, slow start and no power.

 

[dolluper]

Re: Car not running right, RED HOT exhaust

Swap out the fuel filter and do a fuel pressure test,or look at timming a little closer as stated above timing belt maybe,sounds like you have lean condition or late timming

 

[KRS]

Re: Car not running right, RED HOT exhaust

I agree.... check for blockage

 

[one more cast]

Re: Car not running right, RED HOT exhaust

Had this happen on two cars. One was a plugged cat converter and the second was a collapsed exhaust pipe. It was a dual wall pipe and the inside pipe collapsed but you couldn't see it. No power and red hot pipe.

 

[stan_deezy]

Re: Car not running right, RED HOT exhaust

Just a quick thought: Digifant is different from most cars in that the timing has to be set when the revs are in the range 2100-2500. <br />Digifant can be a real pain to set up properly because you have to know the correct method for setting the timing.<br />A quick guide:<br /><br />1. Get the engine hot.<br />2. Stop the engine and set up the strobe timing lamp.<br />3. Start the engine.<br />4. Disconnect the temperature sender (usually coloured blue).<br />5. Rev the engine to 3000rpm at least three times (this sets the ECU into set-up mode).<br />6. Check the timing.<br />7. Reconnect the temperature sensor and reset the idle speed.<br />8. Rev three times to above 2500.<br /><br />Other thought: its the temperature sensor that is faulty: this will send incorrect signal to the ECU causing over-fuelling.<br /><br />Have you checked the fuel pump(s)? 1991 era means you should only have one pump in the tank. The gauze filter in there gets very gunked up.<br /><br />Have you swapped out the fuel filter? Located under the car (if the 1991 is the same in USA as UK!) it seldom gets swapped even when the dealer says he has;trust me I know <br /><br />Check the condition of the Hall Sender in the distributor: these can break up.<br /><br />Check and clean ALL earth straps and connections in the engine bay: these are VITAL in a Digifant: guess what: VW designed the car (by mistake!) so that if an earth strap broke there was an escape route for all that lovely electricity.......straight thru the ECU <br />Imagine that: an electronic brain designed to take 10amps max that could, in theory, take 250 amps if the starter earth failed <br /><br />Let us know how you get on and we can do more head-scratching..................

 

[55Crestliner]

Re: Car not running right, RED HOT exhaust

Forgot to mention in original post - there is ample flow coming from exhaust - gives great pressure on the hand from 2 feet back.<br /><br />I thought about the timing belt jumping, but it's all lined up, and the belt is tight, so I think that's not it.<br /><br />I'm leaning towards the number 4 injector being stuck on, causing a very rich condition in that cylinder. That spark plug is always clean and wet, others are dark. The cat may be trying to burn off a huge amount of fuel.<br /><br />ob - I bet the o2 is fried now, if it wasn't before.<br /><br />others with concerns of blockage - I did still have the same issues when I disconected the cat, and tried to start car - just wouldn't run. And it does get lots of flow out the tail pipe when it is running. But this was my very first thoughts - either that or blocked intake.<br /><br />Thank you all for your thoughts.

 

[55Crestliner]

Re: Car not running right, RED HOT exhaust

I guess I never thought to put a good working Temp sensor in there. I imagine if it's shorted, car will think it's running hot when cold. But that wouldn't put more fuel in would it?<br /><br />How do you check the Hall sender? I did the electrical tests at the harness going to the sender, but no tests to the actual sender.

 

[Dunaruna]

Re: Car not running right, RED HOT exhaust

If you are getting spark, the hall effect sensor is working.

 

[55Crestliner]

Re: Car not running right, RED HOT exhaust

Definately gets spark, all four.

 

[petryshyn]

Re: Car not running right, RED HOT exhaust

Do you get black smoke when it finally starts?<br /><br />I would persue the sticking injector theory. Pull the plugs out, let sit for hour after last crank. Crank the engine looking for excessive fuel expelling from one or more open plug holes. <br /><br /><br />I've seen this on the same vintage of nipendenso injectors.<br /><br />The 02 sensor will not affect starting. Red pipe after cat means rich mixture (likely from a misfire or open injector since its not under load)

 

[55Crestliner]

Re: Car not running right, RED HOT exhaust

No black smoke - more of a heavy colorless fuel smell. My garage now smells like a de-carb job on an outboard.<br /><br />Great idea, I'll take the plugs out and try that. Next step after that I think will be to remove fuel rail, and turn on ignition - see if I'm getting fuel flow.

 

[Bob in Calif.]

Re: Car not running right, RED HOT exhaust

55Crestliner...........<br /><br />Your fuel rail should have a "Schrader valve" of which you can releve the pressure with out removing the fuel rail. That can be tested without having to start the engine, but by just turning the engine over. Make sure you have something to absorb the fuel while discharging it. You might want to check the OHM reading on each of the injectors, with an OHM meter. I'm not sure what the actual OHM reading should be on the VW, but they shouldn't more than 1.5 to 2.0 ohms difference from each other, as I recall. Check your service manual for the normal reading and tolerences <br /><br />You might also check the plug wires for a burnt wire and/or one or more grounding out.<br />My son's Buick had very similar problem's, as to what you are describing. It had a bad injector and a burned and internally broken plug wire. After the replacement of the sour injector and a new set of plug wires, it runs better that ever now.<br /><br />...Bob in Calif...

 

[stan_deezy]

Re: Car not running right, RED HOT exhaust

Here's a few test figures you can use for future reference or if it turns out not be the injector(s) sticking/gummed up (very common once they get older).<br /><br />Throttle Switch (ECU Pin 11) 0.25v @ idle and full load 4.5v @ any other position<br /><br />AIr Flow Meter (ECU Pin 17) 5v supply<br /><br />Coolant Sensor 1-1.5v Cold Engine<br /> 0.2-0.4v Hot Engine<br /><br />Also check the wires going into the injector rail: they are known to get brittle with age.<br /><br />The HT leads may be breaking down: when were they last changed?<br /><br />Also I assume you've cleaned out (and cleaned out again) the throttle body and the idle speed screw orifice?<br /><br />Sticking injector is favourite but these other things are all known problems with Digifant.........although it is a great system when it's running

 

[55Crestliner]

Re: Car not running right, RED HOT exhaust

OK, we're getting somewhere!<br />Thanks to all of the advice, it's much appreciated. <br /><br />The timing is screwy. I have the car running, finally, but it's not right.<br />I did the fuel test, spark plugs out, terminal 3 and 13 bridged (pump running). I looked down the holes, no gas vissible. We can eliminate the injector theory.<br /><br />I just started moving the distributor (advance) a bit at a time, and it finally started. So I get the thing running, no more glowing exhaust. <br />Problem is it will only run with a WHOLE LOT of advance. My timing light with dial was dialed to around 50 advance. <br />(yes, I am doing the Digifant timing correctly - Coolant switch plug off, 2200 rpms, revved to clear etc...) <br /><br />So I thought I'd look at cam timing again, decided it was 1 tooth advanced, based on putting a skinny object down #1 for TDC.<br />Problem is I still don't know for sure where to put an automatics flywheel - there seems to be several marks. So, honestly, I'm just guessing the best I can with the hieght of the piston.<br /><br />Still, it will only run at about 45 advance. It's running, but not smoothly, but it will rev.<br /><br />Here's another clue - on my good working Golf, when connecting the coolant plug, the timing will change. This Jetta will not do that. OH, and also, no change depending on rpm - that whole Digi timing routine doesn't seem to matter to this car.<br /><br />Do I have a distributor issue?<br /><br />Is it time to swap my good computer in again?

 

[dolluper]

Re: Car not running right, RED HOT exhaust

It's possible the distributor shaft is binding in the dist housing causing you to advance so far to get it to run,put #1 cylinder at TDC and mark relationship to block of rotor and pull the distributor out, when out free the shalf up but be carefull not to bend it if it is seized on the housing bushings,Patience and lots of lube[auto trannie fuild works well]