J

jgreenwell

Member
Evening all, first post, so here goes.

Ive got a LR 90 Hybrid, using a shortened RRC chassis with 3.5 V8. The vast majority of it is RRC, so I thought here was the best place to post.

She has started running a little rough. Its a 3.5 V8 EFI on petrol. Starts up fine, ticks over no bother, revs up no probs when standing still. When driving, sometimes its fine, but when you put you foot down a bit, it starts to run rough, missing, spluttering, no backfires though. But ease off the throttle and its ok again, very light throttle seams to be ok.

I have renewed the plugs and leads, just as a matter of course as I didnk know when last done. Removed, cleaned inside the AFM, cleaned up connections etc, all seamed well. I also thought it could be a dirty fuel filter, so tonight removed that and replaced with a bit of pipe to see if that made a difference, but no joy. The filter was dirty, but removing it made no difference.

Has anyone got any ideas? I have the EFi testing manual but not done any voltage checks etc.

Kind regards
Jonathan
 
Have you checked the vac advance unit on the dizzy is operating as thats what does the initial advance when you step on it untill the weights take over this was a problem i had last year but got bigger ones now see oil in the exhaust
 
My 3.5 Efi was cutting out when I put my foot down a few months ago. Turned out to be dodgy earth leads, one to the battery and the one inner wing to engine. Cleaned mine up and re located the one on the wing to a nice clean bit of metal. Also found that under all the grime the one on the wing was hanging by a thread.

Just a thought and easy/cheap to check.
 
Cheers for that folks, I will check those out asap. Funny you should mention earthing points. Everything else works fine (but I guess yours did too), but I do have a very stiff auto gear lever selector. Now I have another to fit that is nice and free, but someone else mentioned that it could be stiff to operate due to it acting as an earth, not sure if this is possible but I will check it out.

Kind regards
Jonathan
 
I had another quick look this morning before leaving for workat the fuel lines. Although I removed the clear plastic carb type inline filter, I thought there should be another one, a metal cylindrical type but I could find it. I will have another look tonight, but should it have one of these fitted?

Jonathan
 
On a more serious note, depending on mileage and history, it could be a stretched timing chain. This will knock your timing out quite significantly, but under no load, revving will be fine but runs RAF when driving. If timing chain is slack, when you replace it do a new camshaft and hydraulic tappets at the same time to save revisiting it after 6 months.
 
Hi all, I didnt have time to have a look last night but will try this afternoon and have another stab at it.

Cheers for the info on the location of the fuel filter on a RRC, mine is however a little different as its a RRC chassis with a Defender truck cab body, so the fuel tank is under the drivers seat. I have followed the fuel lines and there doesnt appear to be another filter, other than the plastic carb one I found.

I have no idea about the mileage of the engine but I dont think its huge. As far as history, recently (last 4 years, since the conversion) she has only been used for trials and a play thing, so little use really. Serviced very regular etc. I have owned her since January, but knew the vehicle as it was a fellow club mambers for around 1.5 years.

I will continue to fault find and fingers crossed its not too expensive.

Kind regards
Jonathan
 
Evening all, just to keep you informed, and to see if anyone can shed some light. I have performed some of the tests in the fault diagnosis manual, and the results are as follows:
Lucas 2AM AFM

Test 6 - Voltage across resistor wire in AFM potentiometer - should be 1.55v - actual 1.55v

Test 7 - Voltage through AFM potentiometer & the wiring to ECU
Step 1 - should be 4.3v +- 0.2v - actual 4.34v
Step 2 - should be 3.7v +- 0.1v - actual 3.72v
step 3 - should decrease to 1.6v -+ 0.1v - actual 1.66v

Test 8 - Ohms - Check internal resistance of AFM and wiring to ECU
............actual readings at.....ECU.....AFM Plug.....AFM socket
Pins 6 & 8 - should be 360K - 396K....395K..........395K
Pins 6 & 9 - should be 560K - 616K....614K..........614K
Pins 8 & 9 - should be 200K - 220K....219K..........219K

Test 9 - Voltage at throttle pot
Step 1 - should be 4.3v - actual - 4.3v
Step 2 - should be 0.325 - actual 0.30v (within tolerance)
Step 3 - should be 4.5v MAX - actual 3.78v

Test 10 - Resistance of air temp sensor in AFM
I didnt have a temp probe so couldnt measure the temp, but measured the resistance and was within the scales provided

Given that the voltages are mostly within tolerance, but the internal resistance of the AFM was quite a way out, how would this effect running, does it look like this could be causing me problems?

Thanks in advance for your help
Jonathan
 
If internal resistance was way out, first and easiest thing is to go to PC World, buy a can of squirty air (actually nitrogen/butane mix) and clean any crap out of it - thats what I do with PC's that have Rare Configuration Disorder. Ignition timing should be checked with a strobe light as any chain stretching will only become apparant when this is done. You've done plugs and leads, but I always change dizzy cap at the same time as it is only a few quid, and pattern part dizzy caps can be a pile of dog c**p and start tracking after about 3 months.

I've a few probs with my 3.9 at the mo, but I think I know what it is. Runs fine on LPG but splutters a bit on Petrol and has symptoms of vapour lock on long journeys. Got another e-mail from Chris at RPI on what to check out next before spending lots of money...
 
Put in a proper fuel filter for EFI set ups! The carb one won't do the job!
Is the fuel pump proper fuel pump for 3.5 EFI?
Check these, as well as the fuel pressure. The actual symptoms you describe in the first message of this thread suggest it's starving on fuel (pressure is not high enough for some reason).

Measure the CTS resistance when car is cold and hot. You can do this also by removing the sensor and putting it under a hot water tap or in a kettle warming up the water. Then you can check the resistance at different temps and see if there is any inconsistency in the readings.

Cleaning the AFM is a good idea, but does not make the same difference as it does with the hotwire AFM.
 
I had cleaned out the AFM a couple of days ago, with some carb cleaner, and also had a look at the track and all seamed well, I will give it another go though. I will also try and find another known good AFM and see how that goes. I take it that the 2AM type is for pre cat, and only that type will work??

Kind regards
Jonathan
 
Well today I tried another AFM and still had the same problems :mad: so its back to the drawing board, but it means that I am going to miss tomorrows RTV!

I will keep you folks updated
Jonathan
 
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