Occasional Stumble and now loud fuel pump

[lotusrepair]

Every now and then as I am taking off from a stop the engine has a stumble. I think the revs are between 3k and 4k. It has happened in 1st and in 2nd gear. It is a quick stumble and then recovery. No fault codes. We just picked the car up 3 weeks ago and I am sorting out its issues. I am not sure where to start looking for this. I drove the car 1/2 hr to a friends house with no problems and then coming back it did it once. I had it happen twice on a short run a week ago.

Chris

[Enright]

I'd primarily suspect electrical rather than fuel, although a bit of Redex in the combustion chambers while you've got plugs out won't hurt (might annoy the neighbours though when you start it and literally rev the cr@p out of it!)

Could be old plugs, arcing of leads, or the very early stages of either failing coil packs or Hall Effect Sensor failure in the CAS.
Start off with the cheapest solution first and work your way up. Take the car out for a drive between each step to check whether you've nailed the problem or introduced more issues, because at least then you've got an idea of what changes you might need to reverse.

1) Get your base timing right.
2) Check plug condition and gaps. Look for any differences between cylinders. Plugs are cheap and you'll need some sooner or later, so get some anyway and try them.
3) Take the leads off and clean them (a rag dipped in paraffin is quite good for this). As you do it, inspect their condition.
4) Coil packs are tricky because there's no outward signs of them breaking down, but if you don't have evidence of them ever having been changed, it's worth getting a set because like plugs, you'll need some eventually. In fact they tend to wear out before leads, but condition of leads is easier to investigate.
5) The hall-effect sensor in the CAS is a similar animal to the coil packs. With both you may just have to put up with it until the intermittent fault becomes frequent enough to give you a fault code.

[John_W]

I agree with Neil, except that I'd swap 4 & 5 as the HES is cheaper than the coil packs, and might be worth swapping just in case. Otherwise, as Neil says you might just have to wait until the intermittent fault becomes more permanent.
John

[lotusrepair]

I have been following the posts about exhaust and boost problems. I had posted previously about a stumble my engine was having about 3K on the revs. As I was reading more I saw that things change after the engine gets above 2900 rpm. With my problem happening between 3000/3500 rpm I started to consider the boost. It only happens now and then but over time I think it is more to do with overboost. Below 2900 rpm I see limited boost and then above that rpm I see boost going to the top of the gauge. This is a recent purchase and we are still working out what was previously done to the car. The of these things was a loud muffler. It is a off the shelf special that was just put on at a local shop. Looking at the pipe bend near the wheel I see a bad kink in the pipe. As with previous threads I see that a sport muffler could cause boost creep. The "notice me muffler" is something I want to change anyway but until the last few weeks I did not know it might be the cause of my problem. The stumble in the engine only happens when accelerating.

is there a way to confirm overboost is the problem? if it is the exhaust I see several options on the SJ site.

Chris

[HJ2]

Actually: there is!

Does the 'check engine' light come on when this happens?
This might help:
http://wikilec.9600.org/index.php/Boost_Creep
and
http://wikilec.9600.org/index.php/CEL
(Code31 should be stored if this is overboost)

From what I can tell now, I am not so sure it is overboost yet, as i would expect it to occur a bit higher in the rev's.
So I would start with this:
http://wikilec.9600.org/index.php/Relea ... _wastegate

Also: Did you change the spark plugs recently? If so: did you gap them correctly?
http://wikilec.9600.org/index.php/Spark_plugs

Good luck!

[rip]

Hi Chris.

Overboost at such low revs could be caused by a sticky wastegate.
Check your ECU error codes though. If you have overboosted, your ECU will know about it. I believe it stores error codes from the last 50 engine cycles, or since its memory was last wiped by disconnecting the battery.

[John_W]

Chris,
If the problem is the stumble or hesitation you mention, this would not make me think of over-boost as the cause. The simplest causes would be incorrect plug gaps or a Hall effect sensor on the way out.

Incidentally, there should be zero boost below 2900 rpm.

John

[lotusrepair]

So far there have been no trouble codes or engine light. I could better explain the stumble as -- during acceleration with the revs going up as gas pedal is applied, there is a sudden loss of engine and then all power is back. You can feel the movement forward in the seat from the loss of power and then the movement back from the engine coming right back to life. If it was just a misfire or a drop in one spark it would feel different. It is the whole engine. That is why I am thinking overboost and the injectors are shutting down all at once. It is like a switch is turned off and then back on.

Another item is that I just changed the air filter in the can to a K+N. The problem happened more often. Is this another sign of boost creep? Could the engine go into overboost and not give a trouble code? I am just thinking that I might need to see if the light bulb is working on the engine light.

Chris

[Brit-Car-Nut]

Look closely at the Wastegate rod travel. If it is only moving a little bit, it will behave as you describe and will mimic the overboost issues found with the oversized exhaust systems.

You should carefully follow the suggestions for the "Wastegate Wiggle" which will basically let you force the wastegate flap thru it's entire travel, not just the beginning stages where it then sticks partially open/closed depending on your point of view.

http://wikilec.9600.org/index.php/Wastegate:_Releasing

The wastegate pivot is a steel spindle in a cast iron housing and rust will form around the pivot and around the seating area of the wastegate flap.

Ironically, a car in South Carolina was having the same issues today (after running crappy for a long time). After replacing the coil packs, the car ran great until 4K then basically shut down because the wastegate rod wasn't moving more than 1/2 inch.

[lotusrepair]

Thanks for the info. I will try the wastegate wiggle as soon as my Elan gets back home. The gas tank is currently being replaced at a shop not far from me. They speak British cars and have a good understanding of Lotus. My lift is a ramp style and the gas tank can not be removed due to the ramp being in the way. Some things you just have to let someone else do.

My 87 Esprit has been suffering from a wastegate sticking closed. I know what overboost and fuel shutdown feels like on a Esprit. PNM is suppose to be making me a new wastegate actuator. Almost done with the Europa repairs and it will free up the lift for another car. A long list of repairs on the cars to get ready for next spring.

Chris

[rip]

a Hall effect sensor on the way out.

It sounds to me more like this than a boost issue.

Overboost will always give a fault code.
A flaky Hall effect sensor is very difficult to diagnose. The only time I have seen it was at around 4000rpm & it felt like the engine did not know what it wanted to do.

[Brit-Car-Nut]

The car in South Carolina did have a bad Hall Effect Sensor which kept putting up error code 41. They replaced it and then the coils which solved the basic crappy running and the error codes but it still slammed into shut down when they hit 4200 rpm. There was never a code set for overboost.

Is it possible he has an modified "MBC" system and the MAP sensor is not recognizing the overboost?

I am not sure why he is getting a new wastegate actuator made since the one used on the M100 is common to the Isuzu, probe, t-bird and the Mazda 626. I was able to pick up a good used one from the local turbo shop.

[Enright]

How much of my list of fault-finding did you get through?
Oh, and you might find it useful to add your location to your profile - you might find someone local who can help (or at least someone in the same timezone, which currently we can't be sure of)!

[HJ2]

At least somebody is paying attention
Next time I'll try to read first, then to answer

[Enright]

At least somebody is paying attention
Next time I'll try to read first, then to answer

Not your problem HJ - I merged these threads because a new one had been started (which quite neatly demonstrates a point I was trying to make).

[lotusrepair]

The wastegate actuator I referred to by PNM was for my Esprit. They seem to be the only ones making a replacement. Lotus makes up most of our collection.

Chris

The car in South Carolina did have a bad Hall Effect Sensor which kept putting up error code 41. They replaced it and then the coils which solved the basic crappy running and the error codes but it still slammed into shut down when they hit 4200 rpm. There was never a code set for overboost.

Is it possible he has an modified "MBC" system and the MAP sensor is not recognizing the overboost?

I am not sure why he is getting a new wastegate actuator made since the one used on the M100 is common to the Isuzu, probe, t-bird and the Mazda 626. I was able to pick up a good used one from the local turbo shop.

[Brit-Car-Nut]

Thanks Chris. I am in the Us (North Carolina) and have a lot of spare M100 bits around. I know nothing about the Esprit, but did any other car use the same turbo set-up? Any chance DBE or Doc Bundy's group in Texas has what you need?
Did you try Dave S. at www.lotusm100parts.com? He has a lot of connections in the Lotus world. There is a fairly large Turbo shop in Concord, NC (Turbo Exchange) that might also be able to help you with the Esprit Turbo parts.

I am assuming you are on the East side of the US since you picked up your car in MD. I get up to Bethesda several times a year, so if you are close, maybe we could meet.

[lotusrepair]

I am in Maryland, northwest of Baltimore. The 80's Esprit share almost nothing in common with the M100. The M100 has a wategate that is part of the turbo. My Esprit has a remote wastegate. The actuator is long out of production. I know all the suppliers in the USA and talk with them each time I see them at LOG. A shame what happened to Dave Bean's home.

I started my Lotus collection in 1991 and am now up to 8 with parts that could build another car or two. I have considered sending the wategate out for rebuild but I am concerned about it getting lost out of state. With no replacements it is hard to mail it out. PNM has been promising to manufacture a replacement they show on their website for about 3 months. I am still waiting. It would be nice to drive the Esprit again. The Europa is almost finished with the brake repairs. The Elite needs a new bearing in the transmission. I tried a rebuilt trans from Lotusbits and it only lasted 4K miles. I like to do most of the work myself and only send out what I have to. Too many bad experiences with shops that made the car worse instead of repairing it. Too many places overcharge for repairs and do not really know how to fix the problem. They hunt and peck away costing more and more money instead of being honest and saying they just do not know how to work on your car. I have found a good shop and they have a factory trained Lotus mechanic. A nice family owned place.

I really enjoy working on cars as a hobby. The car has to interest me technically and be fun to drive. Most of the other cars in the collection are prewar. The M100 is the most modern car in the collection.

Chris

[lotusrepair]

Update:
I think the problem has cleared up. Only a quick drive but it runs better. Replaced the Hall effect sensor. The connector on the existing one had very badly corroded terminals. New connector and new sensor.

More test driving after the 24 to 30" snow storm coming this weekend is over with.

[lotusrepair]

Changed out the fuel tank. We had leaking fuel and it just pointed to a cracked tank. After the tank was put back in the fuel pump is not very load. We replaced the fuel filter while the tank was out. I can feel the vibration in the top fuel line. The car runs fine. I wish I could drive it but the snow is melting and the roads are covered with salt. What would make the pump noisy?

It turns out the tank was not cracked. The inlet hose was the problem. Looks like a poor job when the tank was done under warranty. I now have a spare tank.

Chris